JPH01236248A - Porous film and its production - Google Patents

Abstract

PURPOSE:To improve the extrudability, molding stability, orientability, flexibility, printability, etc., by melt-molding a composition comprising a polyolefin resin, a filler and a specified component and orienting the molding. CONSTITUTION:A composition is obtained by mixing 100pts.wt. polyolefin resin (a) of an MI (ASTM D-1238-70 at 190 deg.C under a load of 2.16kg) of 0.01-10g/10min, which is at least one member selected from among a high- density PE, a medium-density PE and a linear low-density PE or a crystalline PP with 25-400pts.wt. filler (b) of a mean particle diameter <=30mum and 1-30pts.wt. partial ester (c) of dipentaerithritol of a residual OH group content of 3-70%. This composition is melt-molded, and the obtained film is oriented at least unidirectionally at a draw ratio of 1.1 or higher.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a porous film and a method for manufacturing the same.

Specifically, porous films with good appearance and texture, excellent strength, and appropriate moisture permeability obtained by stretching a composition consisting of a polyolefin resin, a filler, and a third component; This provides a method for producing porous films in a stable and highly efficient manner, and such porous films can be used in a variety of applications such as clothing, packaging, packaging materials, battery separators, filtration materials, and sanitary and medical materials. can do.

[Conventional technology and its problems]

BACKGROUND ART Conventionally, there have been many attempts to produce porous films by blending fillers into polyolefin resins and melt-molding the resulting films, which are then uniaxially or biaxially stretched. In recent years, the tear strength has been prevented from decreasing due to stretching orientation.
In addition, various studies have been made to add a third component to obtain a porous film with good appearance and no stretching unevenness at a low stretching ratio.

Further, depending on the application (for example, paper diaper cover sheets), a third component may be used because it is necessary to impart flexibility to the film.

Furthermore, these films are also required to have excellent surface strength, printability (printing ink adhesion and abrasion resistance), and the like.

As a method for improving these drawbacks of conventional porous films, the present inventors proposed polyhydroxy saturated hydrocarbons as the third component in JP-A-58-15538. Furthermore, JP-A No. 61-144331 describes a method using a poly partial ester additive such as adipic acid partial ester or an epoxy-based additive such as epoxidized soybean oil;
10141 and 62-18435 also propose a method using triglyceride, and JP-A-62-129321 proposes a method using silicone oil.

In addition, as a method using ester compounds, JP-A-61
-235439, 62-18435, 62-274
38, 62-280234, 62-280235,
62-288640, 63-22844, etc. have also been proposed.

However, even with methods using these third components, it has not been possible to obtain a porous film that satisfies all properties such as film strength, moisture permeability, flexibility, and printability.

[Purpose of the invention]

The present invention not only has good extrudability when melt molded, but also exhibits particularly excellent molding stability, and the uniaxially stretched film obtained by melt molding has excellent mechanical properties such as tear strength and tensile strength, and moisture permeability. - Both axially oriented and biaxially oriented products have strong surface strength and excellent stretchability.Especially in low ratio stretching, there are very few stretching irregularities caused by non-uniform stretching, and it is highly flexible. It is an object of the present invention to provide a porous film that has excellent printability.

[Structure of the invention]

The gist of the present invention is a porous film obtained by stretching a composition containing a polyolefin resin, a filler, and a third component, wherein the third component has an ○H group ratio of 3 to 70.
% of a partial ester of dipentaerythritol, and a method for producing the same.

The present invention will be explained in more detail below.

As the polyolefin resin used in the present invention, high-density polyethylene, medium-density polyethylene, and linear low-density polyethylene are used alone or as a mixture of two or more, and the melt index of the polyethylene is 0.
．． 01-10g/10min (ASTM D-1238-
70 (measured at 190"C, 2.16 kg). Furthermore, branched low-density polyethylene obtained by a high-pressure method may be partially mixed with the polyethylene.

Crystalline polypropylene is also used. As the crystalline polypropylene, a propylene homopolymer or a copolymer of propylene and other α-olefins may be used alone or in a mixture of two or more. Additives such as heat stabilizers, ultraviolet absorbers, antistatic agents, pigments, and fluorescent agents can be added to these polyolefin resins according to conventional methods.

Inorganic fillers and organic fillers are used as fillers, and inorganic fillers include calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, calcium sulfate, aluminum hydroxide, zinc oxide, and magnesium hydroxide. , calcium oxide, magnesium oxide, titanium oxide, alumina, mica, asbestos powder, glass powder,
Shirasu balloons, zeolite, silicate clay, etc. are used.
Particularly suitable are calcium carbonate, talc, clay, silica, diatomaceous earth, barium sulfate, and the like.

As the organic filler, cellulose powder such as wood flour and pulp is used. These may be used alone or in combination.

The average particle size of the filler is preferably 30μ or less, more preferably 10μ or less, and most preferably 5μ or less. If the particle size is too large, the density of the pores in the stretched product will deteriorate. Surface treatment of the filler is preferably carried out in terms of dispersibility in the resin and further stretchability, and treatment with a fatty acid or a metal salt thereof gives preferable results. The amount of surface treatment with the fatty acid or its metal salt is preferably 10 parts by weight or less per 100 parts by weight of the filler.

If the amount of surface treatment is too large, white smoke or foaming may occur during kneading, granulation, and molding, which is not preferable.

The partial ester of dipentaerythritol used as the third component in the present invention is a partial ester of dipentaerythritol and a carboxylic acid, and representative carboxylic acids include aliphatic mono- or dicarboxylic acids having 1 to 30 carbon atoms and carbon Examples include 7 to 16 aromatic mono- or dicarboxylic acids. Aliphatic monocarboxylic acids are particularly preferred from the viewpoint of moldability and stretchability.

Examples of these are acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, caproic acid, isocaproic acid, 2-ethylbutanoic acid, enanthic acid, caprylic acid,
- Ethylhexanoic acid, nonanoic acid, capric acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, eicosanoic acid, behenic acid,
Examples include aliphatic carboxylic acids such as cerotic acid, melisic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, and sebacic acid, and aromatic carboxylic acids such as benzoic acid, phthalic acid, isophthalic acid, and terephthalic acid.

In the case of a monomolecular partial ester of dipentaerythritol, the above monocarboxylic acids can be used alone or in combination. Further, when dicarboxylic acid is used, it is preferably 0.5 mole or less per mole of cichentaerythritol, and the remaining hydroxyl group is converted into a partial ester by using the corresponding number of moles of monocarboxylic acid.

In addition, the ratio of the number of residual OH groups per molecule of the partial ester of dipentaerythritol is preferably between 3% and 70%, particularly preferably between 3 and 50%.If it is less than 3%, stretchability and printability may deteriorate. The improvement effect is insufficient, and when it exceeds 70%, the film formability deteriorates.

Furthermore, the method for producing a partial ester of dipentaerythritol involves adding a slight excess of carboxylic acid to dipentaerythritol and reacting, stopping the reaction when the target degree of esterification has been reached, and removing the excess carboxylic acid. There is a method of producing a product, and a method of supplying a predetermined amount of raw materials necessary for a theoretical structure and completing a dehydration reaction to produce a product. In the latter case, it is preferable to use an entrainer (water-entraining agent) in order to increase the dehydration effect.

The blending ratio of the polyolefin resin, filler, and partial ester of dipentaerythritol is preferably 25 to 400 parts by weight, more preferably 100 to 300 parts by weight, based on 100 parts by weight of the polyolefin resin. The partial ester of dipentaerythritol is preferably 1 to 30 parts by weight, more preferably 3 to 20 parts by weight.

If the amount of filler added is too small, pores will not be formed sufficiently in the stretched film and the degree of porosity will be reduced.On the other hand, if the amount added is too large, kneadability and dispersibility will deteriorate and the formability of the film will be affected. This results in a decrease in surface strength. In addition, if the amount of the third component is too large, satisfactory crosstalk cannot be obtained.
Film formability and stretchability cannot be ensured.

A common blender or mixer is used to mix the polyolefin resin, filler, and the third component.

As the mixer, a drum, a tumbler type mixer, a ribbon blender, a Henschel mixer, a super mixer, etc. are used, and a high-speed stirring type mixer such as a Henschel mixer is preferable.

Next, the mixture is kneaded using a conventionally known device such as a conventional screw extruder, twin-screw extruder, mixing roll, Banbury mixer 1 twin-screw kneader, or the like.

Molding of the film may be carried out according to a conventional film molding apparatus and method, and inflation molding using a circular die, T-die extrusion molding using a T-die, etc. may be appropriately employed.

The formed film is then stretched, and in the case of -axial stretching, roll stretching is usually employed. Alternatively, it may be in a form in which the -axial direction (drawing direction) is relatively emphasized by tubular stretching. Further, the stretching may be carried out in one stage or in multiple stages of two or more stages.

In biaxial stretching, low-stretching is possible in simultaneous and sequential stretching as well as uniaxial stretching, and at least one direction is 1.
Uniform stretching and porosity can be achieved at 1x.

The stretching ratio at which porosity is achieved and uniform stretching is possible is as follows:
At least one direction is 1.1 to 3.0 times.

Furthermore, the dimensional accuracy of the film can be stabilized by carrying out heat treatment after stretching in both -axial stretching and biaxial stretching.

Further, known surface treatments such as corona treatment and flame treatment can also be performed.

In the present invention, the porous film is 0.01 to 0°5-
1 It is preferably molded to a thickness of 0.02 to 0.3 wa.

[Examples] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Incidentally, a list of raw materials used in the following Examples and Comparative Examples is shown in Tables 1 to 3.

Table-1 (Note) Ml (melt index), ASTM D1
Density measured at 190°C according to 238-70; AST
2 by the density gradient tube method in accordance with M D 1505.
Measurement at 0°C Table-2 Table-3 Number of remaining OH groups: 1 in accordance with JIS K 0070
Yodo Examples 1 to 11, Comparative Examples 1 to 9 The polyolefin resin shown in Table 1 and the filler shown in Table 2 were stirred and mixed in a Henschel mixer, and the third component shown in Table 3 was added thereto and further stirred. A mixture was obtained by mixing. The types and compositions of each raw material component used are listed in Tables 4 and 5.

The resulting mixture was kneaded and granulated using a twin-screw kneader (PCM-45, manufactured by Ikegai Tetsuko), and then inflation molded using a 40-bar extruder under the following conditions to obtain a 65-μ thick raw film. Ta.

Cylinder temperature: 170-190-190”C head, die temperature: 200°C Die diameter: 100 cylinder Blow ratio: 2.0 Take-up speed: 6
m/min The obtained film was uniaxially stretched (longitudinally) at 60°C using a roll stretching machine.

Formability, stretching temperature, and minimum stretching ratio to achieve uniform stretching porosity during pellet production and raw film formation (
Table 6 and Table 7 show the physical properties at λMIN) and λ□8.
Shown below.

Table-4 Table-5 Table-6 Table-7 The methods for measuring moldability and physical property evaluation items are as follows.

(Moldability) 1) Uniform fluidity during film forming of the original film O: Molten resin comes out uniformly from the entire circumference of the die clearance in blown film molding ×: Stable molding is not possible where the molten resin comes out uniformly from the entire circumference of the die 2 ) Bubble stability during film formation on the original film ◎: No bubble sway O: Almost no bubble sway Δ: Bubble sway, but film formation possible According to JIS P-8116, the longitudinal direction of the film (M
D Measure force direction.

Sample size: 63mm width x 76mm length Notch length: 20IIn 2) Moisture permeability According to JIS Z 020B.

However, 30°C 190%RH 3) Flexibility Judgment was made by feeling with the hand according to the following criteria.

◎：Extremely soft O: Soft Δ: A little hard ×: hard 4) Printability (ink adhesion) The evaluation was performed according to the following procedure.

■Preparation of ink Solvent GN50 for diluting Polymate GT (trade name), an ink for untreated polyolefin manufactured by Toyo Ink Manufacturing Co., Ltd.
2, the ink/solvent was diluted to 1/1 (weight ratio).

(3) Solid printing Ink was dropped onto the film, and solid printing was performed using a #8 bar coater (bar coater core diameter 8/1000 inch).

■Drying It was air-dried at room temperature for 24 hours or more.

■ Cellophane tape was adhered to the film coated with cellophane tape adhesive ink while being pressed with a rubber roller.

(2) Judgment of ink adhesion The above-mentioned cellophane tape was immediately peeled off, and judgment was made based on the area ratio of ink remaining on the film.

As can be seen from the comparison between Tables 6 and 7, there is a difference in stretchability and printability between using a partial ester of dipentaerythritol as the third component and when using a complete ester.
When a complete ester of dipentaerythritol is used, even if it can be molded, λ, 8 becomes large, and as a result, the longitudinal orientation of the stretched film increases, resulting in a decrease in longitudinal tear strength.

Further, complete ester (hexaester) has low ink adhesion strength. For this reason, the physical property balance between moisture permeability and strength is poor, and printing and marks may peel off during use.

〔Effect of the invention〕

The method of the present invention includes (1) Porous formation is achieved at a low stretching ratio.

(2) Low stretching stress and low temperature stretching possible.

(3) Uniform stretching is possible at a low stretching ratio.

The resulting porous film has the following characteristics: (1)
Almost no stretching spots are observed.

(2) Excellent moisture permeability, gas permeability, and high water pressure resistance.

(3) Excellent flexibility.

(4) Less anisotropy in physical properties.

(5) High tear strength and tensile strength.

(6) The ink printed on the film has high adhesion strength and abrasion resistance, and has excellent so-called printability.

(7) Good heat sealability and shrink packaging is possible.

(8) There is no bleeding phenomenon of the third component onto the film surface over time, and there is no trouble in printing or other secondary processing. (9) It is easily incinerated and does not generate harmful gases.

It exhibits the following properties and can be applied to a variety of applications including moisture-permeable and leak-proof cover sheets for disposable diapers, clothing, packaging, battery separators, filtration materials, and medical applications.

Person Mitsubishi Kasei Vinyl Co., Ltd. Mitsubishi Kasei Industries Co., Ltd. Agent Patent Attorney Hase - (1 other person)

Claims (2)

[Claims] (1) A porous film obtained by stretching a composition containing a polyolefin resin, a filler, and a third component, the third component being dipenta with a residual OH group ratio of 3 to 70%. A porous film characterized by being a partial ester of erythritol. (2) When manufacturing a porous film by stretching a film obtained by melt-molding a composition containing a polyolefin resin, a filler, and a third component, the residual OH group ratio is 3 to 70 as the third component. A method for producing a porous film, characterized in that a partial ester of dipentaerythritol is used.