JPS61209129A - Manufacture of partially microporous sheet - Google Patents

Abstract

PURPOSE:To form a patterned and partially microporous sheet excellent in permeability to air and moisture, water repellency and tearing strength by a method wherein a sheet, which is made of composition consisting of thermoplastic resin and filler and in which portions different in thickness are distributed both in longitudinal and width directions, is stretched. CONSTITUTION:A thermoplastic resin composition, the thicker portions of which are set to run in the direction normal to the longitudinal direction (extrusion direction) of the sheet of the composition and the thinner portions of which takes 50% or more than the whole area of the sheet, is stretched. The rolling of the sheet is generally done at a temperature, which is lower than the melting point and higher than the secondary transition point of the thermoplastic resin with rolls, preferably with embossing rolls. The shapes of concavities and convexities 1 and 2 engraved on the embossing roll are preferably the pattern, which locates non-rolled portions perpendicular to the weak direction for preventing the propagation of tearing. Next, the rolled sheet is stretched so as to mainly stretch its thinner portion (rolled portion). Further, the resultant sheet is heat-treated under tension and cooled from the drawing temperature down to room temperature in order to be taken off.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing partially microporous sheets. Specifically, a sheet is made of a resin composition consisting of a filler and a thermoplastic resin, and has portions with different thicknesses distributed in the longitudinal direction and the width direction, and the thinner portions are mainly stretched whitened porous portions. Production of a partially microporous sheet with a pattern and excellent air permeability, moisture permeability, water repellency, and tear strength, characterized in that the thick part is stretched so that it becomes a non-stretched (non-porous) part. The present invention provides a method.

(Prior art and its problems) Microporous sheets manufactured by containing inorganic fillers in thermoplastic resins have been widely used for wallpaper, packaging sheets, etc. Taking advantage of its excellent properties such as breathability and water repellency, it has also been proposed to be used in the field of disposable diapers, diaper covers, rain jackets, and other easy-to-use clothing.

A method for producing such a microporous sheet is, for example, a method of stretching a sheet of a resin composition consisting of a polyolefin resin such as polypropylene or polyethylene and an inorganic filler, which is particularly aimed at obtaining a flexible sheet. In some cases, a soft resin such as a thermoplastic elastomer is used, or a softening agent such as a plasticizer is added. After manufacturing such a microporous sheet, a pattern is formed by passing the sheet between press rolls engraved with characters, symbols, figures, etc., or by printing a pattern on the surface of the sheet. It is also proposed that

However, although the stretched microporous sheet as described above has excellent air permeability, moisture permeability, and water repellency, it has low tensile strength and tear strength due to the stretched porosity. Therefore, it is necessary to attach a reinforcing material such as cloth, nonwoven fabric, or film to the obtained microporous sheet, but by attaching the reinforcing material, breathability
Due to the reduced flexibility, there was a problem in using it in the above-mentioned fields such as simple clothing.

(Means for Solving the Problem) The present inventors have developed a stretched microporous film that has excellent tensile strength and tear strength without impairing the properties of a stretched microporous film such as air permeability, moisture permeability, and tΩ aqueous properties, and furthermore We conducted extensive research on a method for producing microporous sheets that have a pattern without any post-production treatment. As a result, it was discovered that the above problem could be solved by stretching a sheet made of a composition consisting of a thermoplastic resin and a filler and having portions with different thicknesses distributed in the longitudinal and width directions, and the present invention. We have come to propose this. That is, the present invention provides a resin composition comprising 20 to 80 parts by weight of a filler with an average particle diameter of 0.1 to 100 μm and 80 to 20 parts by weight of a thermoplastic resin, which has a wall thickness in the longitudinal direction and the width direction. This is a method for producing a partially microporous sheet, which is characterized by stretching a sheet in which different portions are distributed.

The resin composition composed of a filler and a thermoplastic resin used in the present invention is a resin composition mainly composed of a thermoplastic resin and a filler, and additives such as a softener are added thereto as necessary. As the thermoplastic resin used in the resin composition, known ones such as polyolefins such as polyethylene and polypropylene can be used without particular limitation, but polyolefins having a crystallinity of at least 40% or more as determined by X-ray crystallinity measurement. 100 parts by weight of resin (crystalline polyolefin resin) and 5-25% crystallinity, 0.86-
Ethylene and other α with a density of 0.90 g/am3
Compositions comprising 1 to 100 parts by weight of copolymer with olefin are preferred. Further, a soft resin having a low crystallinity of, for example, 10 to 60% can be used alone or in combination with other resins. As the soft resin, for example, a polyolefin thermoplastic elastomer or a composition comprising a polyolefin thermoplastic elastomer and a thermoplastic synthetic resin is preferably used. Representative examples of the polyolefin thermoplastic elastomer include ethylene propylene copolymer (EPR), ethylene-propylene-diene copolymer (RPT), ethylene-butene copolymer, propylene-butene copolymer, etc. , copolymer of olefins,
Alternatively, copolymers of these and Jen, etc. are preferably used. In addition, considering the dispersibility of the thermoplastic resin with the polyolefin-based thermoplastic elastomer, polyolefin-based resins, such as homopolymers and copolymers of olefins such as ethylene, propylene, butene, etc., are generally suitable, and the amount added is also suitable. It is best to use it so that it is less than 50 years old. In addition, the filler is a filler having an average particle size of 0.1 to 100μ, preferably 0.5 to 20μ, especially metal oxides,
Inorganic compounds such as hydroxides and salts are preferably used. Examples of these include calcium oxide, alumina,
Metal oxides such as silica; metal hydroxides such as aluminum hydroxide and calcium hydroxide; calcium carbonate, magnesium chloride, basic magnesium carbonate, calcium sulfate,
Metal salts such as magnesium sulfate and aluminum sulfate; other calcium silicates; cements; zeolites;
Clays such as talc can also be used.

The ratio of the above-mentioned thermoplastic resin and filler is selected depending on the desired air permeability (porosity), tensile strength, etc., but in order to fully exhibit the effects of the present invention, the thermoplastic resin 80%
It is necessary to select 20 to 80 parts by weight of the filler. When the blending amount of the filler is less than the above lower limit, there are few holes formed in the resulting sheet, making it impossible to obtain sufficient physical properties, and on the other hand, when it is greater than the above upper limit, it becomes difficult to restrict the stretching. Not only that, but the physical properties also tend to be insufficient.

As such a composition, in particular in the present invention, (a)
100 parts by weight of crystalline polyolefin resin, X-ray crystallinity of 5-25% and density of 0.86-0.90 g/
100 parts by weight of a mixed resin composition consisting of 1 to 100 parts by weight of a copolymer of ethylene and other α-olefins (b) 50 to 400 parts by weight of an inorganic filler (C) a polyester plasticizer and epoxy At least one plasticizer selected from among plasticizers 0, 1 to 20
Compositions consisting of parts by weight are preferred.

The method for producing a sheet from such a thermoplastic resin composition is not particularly limited, and the composition is mixed and kneaded and then formed into a sheet by a conventional method. The mixing method is generally to mix the powders and granules using a blender or the like, then knead them using an extruder, or mix them in advance using a Banbury Mixer 1 or other melt kneading machine, and then form them into a sheet with or without pelletizing. . In such compositions, flexibility, elongation,
Mineral oil-based softeners, liquid polybutadiene, liquid polybutene, lubricants such as calcium stearate, pigments, heat, light, and other stabilizers, and plasticizers for the purpose of improving mechanical properties such as elastic recovery or moldability. Various additives such as antistatic agents and antistatic agents may also be optionally added. These compositions are formed into sheets by conventional methods.

Generally, sheets are formed by commonly used methods such as calendar molding, press molding, or extrusion molding.
In particular, extrusion molding using a circular die or a tie die is preferred.

The most important feature of the present invention is that a sheet made of the above-mentioned composition is stretched, and the sheet has portions having different thicknesses in the longitudinal direction and the width direction.

Using a sheet in which parts with different thicknesses are distributed in the longitudinal direction and the width direction makes it easy to partially form non-stretched parts (non-porous parts) as a desired pattern during stretching, which will be described later. This is important for preventing a decrease in the mechanical properties of the stretched sheet, such as tensile strength and tear strength, and is completely different from a sheet in which irregular non-stretched portions are formed in a portion of the sheet due to mere stretching unevenness. In the present invention, it is generally practiced to stretch a sheet in which a thick portion is present in a direction perpendicular to the longitudinal direction (extrusion direction) of the sheet, and the area of the thin portion accounts for 50% or more of the entire sheet. be done.

In particular, when it is desired to make the stretching ratio in the width direction larger than that in the longitudinal direction from the viewpoint of sheet physical properties, the thick portions of the present invention are arranged evenly in the longitudinal direction of the sheet before stretching, thereby reducing the tensile strength of the stretched sheet. It can prevent a decrease in strength and tear strength.

The method of distributing portions having different thicknesses in the longitudinal and width directions is not particularly limited, but generally the flat sheet is partially rolled.

The rolling method is generally performed at a temperature below the melting point of the thermoplastic resin and north of the secondary transition point. At this time, in order to roll so that the parts with different thicknesses are distributed as mentioned above,
There is a method in which the sheet is passed through rolls so that there is a part of the unrolled part in a batch process, or a method in which the sheet is passed through rolls with some unrolled parts, or uneven parts (notches) such as letters, figures, patterns, etc. are formed on the surface of one of a set of upper and lower rolls. ) There is a method in which the sheet is continuously passed between rolls provided with so-called embossing rolls, etc., but a method using an embossing roll is particularly preferred. The shape of the embossed part of the embossing roll is selected as appropriate and may be calculated in advance based on the rolling ratio, the stretching ratio, the size of the pattern of the product, etc., but it is generally preferable to have a shape in which the non-rolled part is dispersed in the rolled part. . In addition, the shape and size of the unevenness of the rolling part (pressing part) and non-rolling part (non-pressing part) of the embossing roll can be arbitrarily selected.
Generally, the convex portions are dotted with concave portions, and the area of the convex portions on the roll surface is 50% or more of the total area, preferably 60% to 60% of the total area.
Furthermore, as shown in Fig. 1, the shape of the concave portion is a rectangular rectangular parallelepiped with a height of about 100 μ, and the concavities and convexities are arranged in a small and intricate manner, in order to uniformly perform the stretching described later. This is preferable because a sheet having an intentional pattern of stretched and non-stretched areas can be easily obtained even at a low magnification without requiring a special dispersant formulation.

Specific examples of embossing rolls include combinations of metal/metal rolls and metal/rubber rolls, etc. In this roll, an uneven pattern is engraved on one metal roll, and the sheet before being stretched is pressed between the rolls on the opposite side. Generally, metal/rubber rolls are easy to handle and can be used.

In addition, the shape of the unevenness engraved on the embossing roll is as follows:
Examples include those shown in Figures 1, 2, and 3. In particular, when the main purpose is to prevent a decrease in tear strength, the unrolled part is positioned perpendicular to the weak direction to prevent tear propagation. Patterns are preferred.

The degree of rolling is not particularly limited; however, if the pressure is too low, little effect will be exerted, and if it is too high, the sheet may be damaged and cut during the next stretching operation, making stretching difficult. , the desired effect can be achieved depending on the degree of softness of the resin (it may be determined in advance,
Generally, it is carried out at a linear pressure of about 10 to 100 kg/cm2.

Next, parts with different wall thicknesses are distributed (rolled)
The sheet is stretched so that the thin part (rolled part) is mainly stretched. Stretching is generally carried out uniaxially, if necessary biaxially, at a temperature above room temperature and below the melting point of the resin to an area magnification of 1.2 times or more, preferably 1.5 to 3.0 times. Furthermore, it is generally preferable to carry out a heat treatment under tension following the stretching process, and then cool the film to room temperature below the stretching temperature and take it out. By doing so, a sheet having a pattern having porous portions (stretched portions) and non-porous portions (non-stretched portions) can be obtained. In this case, it is preferable that the area of the stretched portion be one-half or more of the entire sheet, and if it is less than this value, it is difficult to obtain the desired air permeability.

(Functions and Effects) According to the present invention, the longitudinal-lateral (lengthwise-widthwise) stretching ratio can be arbitrarily selected depending on the required physical properties such as mechanical strength; ) A higher stretching ratio in the direction causes less breakage and facilitates continuous production. However, the stretched sheet obtained at this time has weak tear strength in the longitudinal direction and tensile strength in the transverse direction, so the sheet used in the present invention generally has thick portions partially in the direction perpendicular to the longitudinal direction. Specifically, it is preferable that rolling is performed using rolling rolls that repeatedly leave non-rolled portions in a direction perpendicular to the longitudinal direction, and in particular, non-rolled portions arranged so as to increase tear resistance. Preferably, rolling is carried out using a rolling roll having a diameter of 100 mm. In the sheet obtained in this manner, where parts with different wall thicknesses are distributed, microvoids are generated at the interface between the resin and the filler in the thin part of the sheet, and the thin part becomes preferentially stretch-whitened ( porous)
Then, the thick part is stretched, or by adjusting the stretching ratio, the thick part can be left almost as an unstretched part. Therefore, the obtained stretched sheet has thin portions (non-porous portions) formed in the desired pattern, and a decrease in tear strength in the longitudinal direction and tensile strength in the transverse direction can be prevented. Another effect of the present invention is that thin/thick parts are present at small intervals in the sheet before stretching, which facilitates low-magnification stretching and improves air permeability and i3? While having the functions of a microporous sheet such as ff properties,
The effect of suppressing the deterioration of physical properties due to stretching and porosity is exhibited.

(Example) Examples and comparative examples will be shown below, and physical property measurements in the present invention were performed by the method described below.

Tensile strength (T, S) and elongation at break (Eb): Measured using a tensile tester (Tensilon: Toyo Baldwin) at 25° C. at a speed of 200 m/min using a No. 1 dumbbell.

Example 1 and Comparative Example 1 Linear low-density polyethylene (product name: Urtozex 20
20 L, density (ρ) = 0.92, melt flow index (MFT) = 2゜0) to 100 parts by weight of ethylene-butene-1 soft resin (trade name: Tafmer A409)
0, ρ = 0.88, MFI = 3.6) and 100 parts by weight of a mixed resin composition consisting of 50 parts by weight of heavy calcium carbonate (
Product name: Whiten SSB, average particle size 1.2μ, Shiraishi Calcium Co., Ltd.) 150 parts by weight and polyester plasticizer (
After extrusion molding a mixed resin composition consisting of 3 parts by weight of Volisizer W-2300DrC (trade name: Volisizer W-2300DrC) into a sheet with a thickness of 55 μm, the pattern as shown in FIG.
X l ** (thickness approximately 100μ), the concave portions are arranged at an interval of 2 squares from the convex portions both vertically and horizontally, and the area of the convex portions (rolled portions) is 76% of the total area. After rolling at room temperature, it was stretched twice at room temperature and then heat treated in an oven at 90°C. The obtained sheet was a patterned sheet in which the rolled portion was whitened as shown in FIG.

In addition, as a comparative example, the same sheet was sandwiched between flat metal rolls and rolled, and then a sheet was similarly uniformly stretched twice.

The results of measuring the physical properties of the obtained sheet are shown.

It was found that the patterned microporous sheet according to the present invention has particularly excellent tear strength compared to the comparative example, and is a microporous sheet that has moisture permeability and waterproof ability suitable for use in simple clothing as well as surface decoration. be.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are schematic diagrams showing the surface condition of the embossing roll. In the figure, 1 is a concave portion and 2 is a convex portion. Patent Applicant Atsushi Tokuyama Soda Co., Ltd. Figure 2 Figure 3 Procedural Amendment April 9, 1986 Director General of the Patent Office Michibe Uga I, *Indication of Patent Application No. 38794-2, Invention Title: Method for manufacturing partially microporous sheet 3, Interaction with the case of the person making the amendment Patent applicant address: 1-1-4 Mikage-cho, Tokuyama-shi, Yamaguchi Prefecture, r invention of the specification subject to amendment Column 5, "Detailed explanation of", contents of correction (Reference 31) tIF, page 4, lines 1-2, "in polyolefin resin" is corrected to "polyolefin resin". (2) On page 10, lines 5-4 from the bottom, "on average" is corrected to "parallel." (3) On page 13, line 5, correct r kg/cv/J to rkg/cwJ. (4) On the bottom line of page 14, “thin wall portion” is corrected to “thick wall portion”. (5) Insert the table of contents in the fifth line from the bottom of page 15. "Tear strength: Based on JIS L 1005/l single tongue method, 4c+++llXl
Measurements were made using a sample with a length of 5c+w. Moisture permeability: JIS Z at 25℃ and 90% relative humidity
Measured in accordance with 0208. ” (6) Same page 16, line 7, rD I CJ is corrected to “r large mouth water ink (Hayashi)”. that's all

Claims (1)

[Scope of Claims] (1) Filler with an average particle diameter of 0.1 to 100μ 20 to 80
parts by weight of a thermoplastic resin and 80 to 20 parts by weight of a thermoplastic resin, and is characterized by stretching a sheet in which parts with different thicknesses are distributed in the longitudinal direction and the width direction. A method for producing a sheet having microporosity. (2) The thermoplastic resin has 100 parts by weight of a polyolefin resin that has crystallinity of at least 40% or more as determined by X-ray crystallinity measurement, and 0.86 parts by weight of a polyolefin resin that has crystallinity of 5 to 25%.
Ethylene and other α with a density of ~0.90 g/cm^3
A method for producing a microporous sheet according to claim (1), characterized in that the copolymer with olefin is comprised in an amount of 1 to 100 parts by weight. (3) By partially rolling a flat sheet of the resin composition using rolls with uneven surfaces, a sheet with different thicknesses distributed in the longitudinal and width directions is stretched. A method for producing a microporous sheet according to claim (1). (4) A resin composition consisting of a filler and a thermoplastic resin contains (a) 100 parts by weight of a crystalline polyolefin resin, a crystallinity of 5 to 25% by X-rays, and a density of 0.86 to 0090 g/cm^3. 100 parts by weight of a mixed resin composition consisting of 1 to 100 parts by weight of a copolymer of certain ethylene and another α-olefin (b) 50 to 100 parts by weight of an inorganic filler
400 parts by weight (c) At least one plasticizer selected from polyester plasticizers and epoxy plasticizers 0.1 to 20 parts by weight
The manufacturing method according to claim (1), which consists of parts by weight. (5) A method for producing a microporous sheet according to claim (1), using sheets having different thicknesses in which the thin portion accounts for 50% or more of the whole.