JPH04202442A - Porous sheet - Google Patents

Abstract

PURPOSE:To achieve a high biodegradability and enable a spontaneous degradation in a relatively short time by stretching a sheet obtd. by melt molding a compsn. contg. a polyolefin resin, a specific filler, and other necessary additives. CONSTITUTION:100 pts.wt. polyolefin resin (e.g. PE) is mixed with 20-250 pts.wt. filler comprising 100 pts.wt. inorg. filler having a mean particle diameter of 5mum or lower (e.g. CaCO3) and 5-100 pts.wt. biodegradable org. filler having a mean particle diameter of 10-40mum (e.g. starch) and 0.5-30 pts.wt. additives such as a surface-treating agent, an antistatic agent, a plasticizer, and a lubricant. The resulting compsn. is melt molded to give a sheet, which is then stretched in an area stretching ratio of at least 1.5, giving a porous sheet having a moisture permeability of 0.7-3.2g/100cm<2>.hr.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a porous sheet (the porous sheet referred to in the present invention also includes a porous film), which is particularly highly biodegradable and easily disintegrated. Regarding porous sheets.

[Problems to be solved by conventional techniques and inventions] In recent years,
There is an increasing demand for microbial degradability for plastics, but Japanese Patent Application Laid-Open No. 54-119593
As typified by the inventions described in JP-A-119594 and JP-A-54-119595, materials based on the approach of novel copolymers are currently not available due to problems with their physical properties or production technology. Practical application has not yet been established. Therefore, plasting, which is currently considered to have microbial degradability, has among its components:
The reality is that practical use is limited to products that are filled with a composition that is disintegrated by microorganisms at a certain blending ratio to ensure microbial decomposition.

On the other hand, considering the disintegration properties of films again, the surface of the film is usually coated with a resin, that is, a plastic material, and therefore it is easy to see that the time required for the disintegration of the film is enormous. It can be estimated that it takes about half a year to go fishing on a boat.

Therefore, porous sheets are used in disposable body fluid absorbent products, especially disposable diapers that are intended for large amounts of exudate, in order to prevent stuffiness, rash, itching, etc. during use. However, if a porous sheet used as a leak-proof sheet is used in disposable products such as disposable diapers and then discarded and left in a landfill without being incinerated, the porous sheet may If it is made of conventional plastic film, it is unlikely that it will naturally disintegrate under normal conditions, and even under favorable conditions where it can disintegrate, it is clear that it will take an extremely large amount of time to disintegrate. It can be easily assumed that this will leave concerns about the future as a global environmental problem.

Therefore, an object of the present invention is to provide a porous sheet that is highly biodegradable and easily disintegrates naturally in a relatively short period of time when disposed of without being incinerated.

[Means for Solving the Problems] As a result of various studies to achieve the above object, the present inventors have found that in order to achieve more efficient disintegration properties, the film is subjected to a stretching process after being formed. By making the film porous, the surface area of the film itself that can come into direct contact with microorganisms in the soil is increased, and as a filler for the film, a highly biodegradable organic material is used in combination with an inorganic filler to make the film porous. It was found that the adhesive sheet has early disintegration properties.

The present invention was made based on the above knowledge, and after melt-molding a stretched porous sheet composition in which a polyolefin resin is mixed with a filler and other additives to form a raw sheet, the raw sheet is In a porous sheet obtained by stretching the sheet at an area stretching ratio of at least 1.5 times, the amount of the filler mixed in is 2 parts by weight per 100 parts by weight of the polyolefin resin.
0 to 250 parts by weight, and the filler is inorganic filler 10
0 parts by weight and 5 to 100 parts by weight of an organic filler, the organic filler being movable and disintegrating with a knife.

Hereinafter, the porous sheet of the present invention will be explained in detail.

In the following description, a porous sheet with moisture permeability suitable as a leak-proof sheet in a "disposable body fluid absorbent article" will be mainly described, but it should be noted that the porous sheet of the present invention is not limited to its uses. Not until now.

The polyolefin resin in the present invention includes monoolefin polymers such as ethylene, propylene, butene, copolymers thereof, and mixtures containing the above polymers and copolymers as main components, such as high-density polyethylene,
Examples include low density polyethylene, linear low density polyethylene, polypropylene, ethylene-propylene Bronok copolymer, polybutene, ethylene-vinyl acetate copolymer, and mixtures thereof. In the case of a porous sheet for disposable diapers, it is preferable to use flexible and tough linear low-density polyethylene.

In addition, as the filler in the present invention, an inorganic filler and an organic filler are used in combination, and examples of the inorganic filler include carbonate, barium sulfate, talc, gypsum, clay, kaolin, NoriKiki, UilK soil, and carbonate. Magnenium oxide, Magnenium phosphate, Magnenium phosphate, Aluminum hydroxide,
Examples include zinc oxide, titanium oxide, alumina, mica, zeolite, carbon black, etc. Organic fillers include those that are biodegradable, such as TJ and FAR that are processed into powder and have biodegradability. Preferred examples include soybean, cornstarch, multi-FIG, and cellulose.The fact that these organic fillers are biodegradable is described in Japanese Patent Publication No. 53-23864, This is a well-known fact from Publication No. 512153.0, Japanese Patent Publication No. 53-46199, etc.

Other additives used in the present invention include surface treatment agents used for uniform dispersion of the above-mentioned inorganic and organic fillers and the above-mentioned polyolefin resin, as well as commonly used antistatic agents and plasticizers. , lubricants, stabilizers, ultraviolet absorbers, etc., as well as additives to easily develop moisture permeability and maintain a supple texture when the porous sheet is used for "disposable body fluid absorbent articles". One or two of various additives used in the production of porous sheets, such as
Contains more than one species. In addition, in the present invention, the above-mentioned surface treatment agent includes fatty acids or their metal compounds, Nran-based,
Although it is possible to use general compounds known to contribute to the uniform dispersibility of fillers in resins, such as titanium-based camping agents, it is preferable to use compounds that can make the surface of the filler hydrophobic. In addition, as additives to easily develop moisture permeability and impart a supple texture, representative examples of ester compounds are listed in addition to liquid polybutadiene, liquid polyisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, etc. Preferred specific polyesters include polyesters in which carboxylic acids or alcohols at both ends of a polyester of noethiolene glycol and dimer acid are partially or completely blocked with stearyl alcohol or stearic acid, 1,3-butaneol and anopine. Polyester in which both ends of acid polyester are capped with hydroxystearic acid, hexaester consisting of trimethylolpropane-adipic acid-stearic acid, octaester consisting of pentaerythritol-adipic acid-stearic acid, dipentaerythritol-adipic acid-stearin Examples include dodeca ester consisting of an acid, polyester using dimer acid or hydrogenated dimer acid instead of adipic acid, which is a constituent component of the polyester, and polyester using isostearic acid instead of stearic acid.

The preferred blending ratio of the stretched porous sheet composition for obtaining the porous sheet of the present invention is 10 parts polyolefin resin.
0 parts by weight, 20 to 250 parts by weight of the filler and 0.5 to 30 parts by weight of other additives. Among the fillers, the blending ratio of the biodegradable organic filler to 100 parts by weight of the inorganic filler is 5 to 100 parts by weight. The inorganic fillers here particularly contribute to the formation of the porous sheet, and the organic fillers contribute to the biodegradability of the porous sheet. If the amount of organic filler added is less than the above range, the microbial degradability will not be noticeable, while if it is added too much, problems such as retention deterioration during melt molding will occur. In addition, it is desirable to use an inorganic filler with an average particle size of 5μ or less,
The reason for using such fine particles is that it is necessary to make the sheet porous after stretching and to maintain sheet strength. On the other hand, it is desirable to use an organic filler with an average particle size of 10 μm or more and 40 μm or less, and the reason for using such a filler is to balance the porosity and strength, and to reduce the decomposability of the sheet after it is disposed of. This is because it is formulated with living organisms in mind.

A general blending method is sufficient for uniformly mixing the above-mentioned stretched porous sheet composition. It is more preferable to melt and knead the composition using a shaft press ratio machine, mixer roll, heat mixer, etc., and then process the composition into a sheet by melt molding to obtain a raw sheet. For melt molding, a general sheet molding method can be used, and any method such as an inflation method, a T-diflant method, or a calendar method may be used. However, in consideration of the deterioration of the organic filler, it is desirable to perform the molding at as low a temperature as possible.

The porous sheet of the present invention can be obtained by stretching the raw sheet obtained as described above to make the sheet porous. The stretching method at this time is not particularly limited, and there is no problem as long as it is a method suitable for making it porous, such as uniaxial stretching typified by roll stretching, tender stretching, mandrel stretching, etc. There is no problem in using any method such as sequential or simultaneous biaxial stretching using a combination of the above. However, when tubular biaxial stretching is used, the stretching stress is reflected in the air pressure, so in order to keep the internal pressure constant, this stretching method produces porous sheets with high moisture permeability, i.e. It is not a very desirable method for processing of 200 Og/n (24 hours or more) such as those used for disposable diapers.

The stretching ratio varies depending on the formulation and the selection of the stretching method, but in order to achieve uniform porosity, an area stretching ratio of 1.5 times or more is required, and an area stretching ratio of 16 times or less is desirable. .

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 5 and Comparative Examples 1 to 3 Using a composition consisting of the following [raw materials] and having the composition shown in Table 1 below, the following [raw material kneading] step, the following [raw sheet forming] step, and Each porous sheet was obtained through the following (stretching) process.

The physical properties of each of the obtained porous sheets evaluated by the following [Physical Property Evaluation] are shown in Table 1 below.

[Raw materials] ■Polyolefin resin cotton-like low-density polyethylene resin (■ in Table 1) Tsurtosenkusu 221L manufactured by Mitsui Petrochemical Industries ■Inorganic filler natural calcium carbonate (average particle size lμ, Table 1) Rydon 2200 manufactured by Kitafunka Kogyo ■ (surface treated with fatty acid) ■ Organic filler corn starch (average particle size 20μ, ■ in Table 1) ■ Additives that contribute to stretching Polyester shown below (■ in Table 1) TMP nitrimethylolpropane AA, adipic acid [Kneading of raw materials] The inorganic filler (1) and the organic filler (2) were placed in a heating stirring device, and then sufficiently surface treated in a heated state. after that,
Resin (1) and additive (2) contributing to stretching were added and uniformly premixed using a Hennel mixer. Next, this was melted and kneaded using a twin-screw extruder (PCM-45 extruder, manufactured by Ikegai Iron Works), followed by water cooling, cutting, and drying steps.
Pellets in which the raw material was uniformly dispersed were obtained.

[Formation of raw sheet]

Using the pellets obtained in the above kneading process,
Melt sheet molding was performed using 0m single screw extrusion II (width 500sn coat hanger T die), and the basis weight was 70g/n.
(Original fabric sheet was obtained.

[Stretching]

In the case of uniaxial stretching, the raw sheet obtained in the above forming process is stretched in the longitudinal direction using a roll stretching machine (width 700 m).
In the case of biaxial stretching, simultaneous biaxial stretching in longitudinal and lateral directions was performed using a simultaneous biaxial stretching machine using a tenter method to obtain a porous sheet.

〔Evaluation of the physical properties] Moisture permeability: Based on JIS z-o2os.

Evaluation of biodegradability: Since the evaluation method has not been established as a general method, longitudinal tearing of the sheet was determined by measuring the strength immediately after molding and the value obtained by measuring the strength for 3 months afterward according to JIS P-8]16. The biodegradability was evaluated based on the rate of decrease by comparing the values measured after burying the sample in leaf soil.

Table 1 As is clear from the results shown in Table 1 above, the porous sheet containing biodegradable cornstarch was more effective than the porous sheet containing no organic filler (Comparative Examples 2 and 3). It can be seen that strength reduction is accelerated.

As shown in the examples of the present invention, a porous sheet obtained by using natural calcium carbonate as an inorganic filler and natural corn starch as an organic filler has the following properties:
It also has the potential to be decomposed and used as compost.

C Effects of the Invention] The porous sheet of the present invention has high biodegradability, and when disposed of without being incinerated, it easily disintegrates naturally in a relatively short period of time.

Claims (3)

[Claims] (1) After melt-molding a stretched porous sheet composition in which a filler and other additives are mixed with a polyolefin resin to form a raw sheet, the raw sheet is stretched at an area stretching ratio of at least 1.5 times. In the porous sheet obtained by stretching, the amount of the filler mixed is 20 to 250 parts by weight per 100 parts by weight of the polyolefin resin, and the filler is 100 parts by weight of an inorganic filler and 5 to 5 parts by weight of an organic filler. 100 parts by weight, and the organic filler is a biodegradable organic substance. (2) Moisture permeability is 0.7-3.2g/100cm^2・h
The porous sheet according to claim (1), which is r. (3) The porous sheet according to claim (1), wherein the organic substance is starch, cornstarch, pulp powder, or a mixture thereof.