JPH0546851B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a moisture-permeable film, and more specifically, the present invention relates to a moisture-permeable film, in which a thermoplastic resin having low compatibility with the polyolefin resin (hereinafter referred to as additive resin) is mixed with a polyolefin resin. The present invention relates to a polyolefin-based moisture-permeable film produced and stretched, and a method for producing the same.

(Prior art) Conventional methods for manufacturing moisture permeable films include perforating a non-porous film by electric discharge machining, adding calcium carbonate particles during film formation, and
A method in which the calcium carbonate is eluted by acid treatment to form a porous film, a method in which inorganic fine particles such as calcium carbonate are added during film formation to form a film, and the film is stretched uniaxially or biaxially;
A method has been implemented in which two types of resins with low compatibility are kneaded to form a film, and then stretched uniaxially or biaxially.
Of these, the first two are unfavorable in terms of productivity, and a method of stretching a film to which inorganic fine particles have been added is generally used.

(Problems to be Solved by the Invention) However, porous films obtained by stretching films to which inorganic fine particles have been added tend to have high rigidity due to the high stiffness of the filler, and When this happens, the filler tends to fall off, resulting in poor usability, and depending on the application, the filler that falls off becomes dust, which may impair environmental conditions.

In addition, there is a method of kneading two types of resins with low compatibility and stretching the mixture, for example,
12542 and Publication No. 198536, etc., these methods have various drawbacks.

That is, in the former (Japanese Patent Publication No. 53-12542), 0.05 to 10% by weight of polystyrene is mixed with polypropylene, and the film is formed and stretched to obtain a film with internal air bubbles. As a result, cavities are generated from the surface to the inside, but it is pointed out that not only the amount of cavities that are generated is reduced, but also that it becomes difficult to stretch the molded product.

Furthermore, in the case of a film formed by simply kneading a polyolefin resin as a base resin and a polystyrene resin as an additive resin, the polystyrene resin, which is in the form of fine particles, is deformed during film formation, resulting in poor stretchability. However, even if it could be stretched, the pore size would be too large and the waterproofness would be poor, or
The pores are layered and not continuous, resulting in a film with low air permeability and low moisture permeability.

On the other hand, in the latter (namely, JP-A No. 58-198536), the base resin (A) has a melting point of 20
The additive resin (B) with a temperature higher than ℃ is kneaded at a temperature higher than the melting point of B, and formed into a sheet at a temperature between the melting points of A and B.
A porous film is obtained by stretching at a temperature lower than the melting point of the film, but during film formation, the added resin coagulates when solidified, increasing the particle size and increasing the pores after stretching, resulting in excellent waterproof properties. It is difficult to obtain film.

Furthermore, if polyethylene is used as A and polybutylene terephthalate, polycarbonate, etc. is used as B and melt-kneaded at a temperature higher than the melting point of B, there is also the drawback that thermal deterioration of the polyethylene occurs and the strength of the resulting film decreases.

(Means for Solving the Problems) As a result of intensive studies in order to eliminate the above-mentioned drawbacks, the present inventors have developed a method for forming a film under specific conditions using a polyolefin resin and an additive resin with a higher melt viscosity. The present invention was achieved by discovering that a porous film can be efficiently obtained by stretching.

That is, the present invention provides polyolefin resin (A)
and a thermoplastic resin (B) with low compatibility with the polyolefin resin are essential components, and A and B are at a temperature of 200°C.
The ratio of apparent viscosity measured at a shear stress of 4.5 × 10 ⁵ dyne/cm ² at °C is B / A = 2 to 100,
And 10 to 100 parts by weight of B are melt-kneaded to 100 parts by weight of A to form a film under conditions where the resin temperature immediately after exiting the die is 220°C or less, and the cooled unstretched film has a maximum surface temperature of 30°C in the stretching zone. ~110℃
The moisture permeability obtained by stretching 1.2 to 10 times in at least one axis under ^the conditions of
Concerning a moisture-permeable porous film with atmospheric pressure and water pressure resistance of 50 cmAq or more.

Examples of the polyolefin resin used in the present invention include linear low-density polyethylene, high-pressure low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymer,
Examples include, but are not limited to, ionomer resins.

Examples of additive resins used in the present invention include polystyrene (general grade, heat-resistant grade, and impact-resistant grade), acrylonitrile-styrene copolymer, butadiene-styrene copolymer, acrylonitrile-styrene copolymer, and acrylonitrile-styrene copolymer.
Examples include amorphous resins such as butadiene-styrene copolymer, polymethyl methacrylate, and cyclohexanedimethanol-modified polyethylene terephthalate copolymer.

In order to efficiently obtain a moisture-permeable film, it is necessary to prevent the added resin fine particles, which have been turned into fine particles by melt-kneading, from being deformed during extrusion film formation. That is, temperature 200℃, shear stress 4.5×
The apparent viscosity of the additive resin measured under the condition of 10 ⁵ dyne/cm ² needs to be 2 to 100 times the apparent viscosity of the polyolefin. If the apparent viscosity of the added resin is less than 2 times, the viscosity difference during melt-kneading becomes even smaller, and the particle size of the added resin becomes too small, which not only reduces moisture permeability but also reduces the shear rate of the kneading section. If this becomes large, film forming properties will be extremely deteriorated, such as an inversion phenomenon of melt viscosity occurring.

On the other hand, if the viscosity ratio is 100 times or more, the kneading becomes insufficient and the particle size of the added resin particles becomes large. However, because the pore diameter of the moisture-permeable film obtained is large, only a film with extremely poor waterproof properties can be obtained.

In addition to the above polyolefin resins and additive resins, liquid polybutadiene, liquid polybutene, liquid polyisoprene and derivatives thereof, polybutene-1, ethylene-propylene-diene terpolymers, ethylene-propylene random copolymers , ethylene-butene radum copolymer, polybutadiene resin, and ethylene-vinyl acetate copolymer, one or more selected from the group consisting of 100 parts by weight of polyolefin resin,
It can be added in an amount of 55 parts by weight or less.

If it exceeds 55 parts by weight, not only the film formability but also the stretchability will deteriorate, making it impossible to efficiently produce a moisture permeable film.

Furthermore, in addition to the above-mentioned resins, commonly used heat stabilizers, slip agents, antiblocking agents, colorants, antistatic agents, etc. can be added.

Further, inorganic fine particles such as calcium carbonate may be added as necessary for the purpose of matting or the like.

The steps for producing a moisture permeable film using the method of the present invention will be explained below.

First, a predetermined amount of additive resin having a predetermined apparent viscosity is mixed with a polyolefin resin and melt-kneaded at a temperature that allows for kneading, and then a film is formed under conditions where the resin temperature immediately after exiting the die is 220 ° C. or less, Cool to obtain an unstretched film.

At this time, it is necessary to mix 10 to 100 parts by weight of the additive resin with respect to 100 parts by weight of the polyolefin resin.

If the amount is 10 parts by weight or less, as stated in Publication No. 53-12542, pores will not be formed to the surface and 1000
g/m ² / 24 hours / atmospheric pressure, it is difficult to make a moisture permeable film.

On the other hand, if it exceeds 100 parts by weight, a reversal phenomenon between the polyolefin resin, which should be a matrix phase, and the additive resin, which should be made into fine particles, tends to occur, and no pores are generated even when stretched, resulting in a moisture-permeable film. I can't.

If the resin temperature immediately after exiting the die exceeds 220°C, the viscosity difference between the polyolefin resin and the additive resin becomes small, the deformation of the additive resin increases, and the alignment of the additive resin in the drawing direction causes a decrease in stretchability, especially Not only is stretching in the longitudinal direction difficult, but the pores become layered and the continuity rate in the thickness direction of the film decreases, so that only a film with low moisture permeability can be obtained.

It should be noted that the same applies not only to extrusion film forming but also to film forming by a calendar method, and if the resin temperature during molding is 220° C. or lower, a good unstretched film for a moisture permeable film can be obtained.

The unstretched film thus obtained is stretched in at least one direction so that the maximum surface temperature of the film in the stretching zone is in the range of 30 to 110°C, preferably in the range of 60 to 100°C. In this case, if the temperature is 30° C. or lower, neck stretching tends to occur, resulting in poor uniformity, and equipment troubles are likely to occur due to high stretching tension.

On the other hand, if the temperature is 100° C. or higher, the stretching tension becomes too small, resulting in poor stretching stability and frequent breakage. Furthermore, since the added resin also deforms,
Since no pores are generated, it cannot become a moisture permeable film.

Stretching magnification is 1.2 to 10 times, area magnification is 1.2 to 40
It is preferably within the range of 2 times, and may be appropriately selected depending on the desired moisture permeability. Although it is possible to increase the area magnification by 40 times or more, in this case, the pores generated will become too large, depending on the particle size of the added resin, resulting in poor waterproof performance with water pressure resistance of 50 cmAq or less. On the other hand, if it is less than 1.2 times, it is difficult to uniformly stretch it and make it porous.

The stretched film can be heat set if desired. The heat fixing conditions may be 1 to 20 seconds at a temperature of 70° C. or above and below the melting point of the polyolefin resin -5° C., but it is also possible to enlarge or reshape the shape of the pores by performing the treatment for a longer time.

(Functions and Effects) In the present invention, when a thermoplastic resin having low compatibility with polyolefin is added to a polyolefin resin and then heated and melted and kneaded, both resins are macroscopically mixed, but microscopically separated and form a film. is formed into.

When this film is stretched at an appropriate temperature, it is thought that a part of the separated interface will peel off and that part will open, creating micropores.

Further, the particle size of the added resin can be changed by adjusting the temperature of heating and melting during kneading and the degree of kneading. Furthermore, by adjusting the stretching ratio, the size of the generated micropores can be changed.

Due to the above-mentioned effects, the method of the present invention does not require the addition of inorganic fine particles to the thermoplastic resin unlike the currently widely used methods, so there is no problem of fine particle scattering during processing and the moisture permeability achieved is In the film, the additive resin particles are in close contact with the polyolefin resin in some parts, so that they do not fall off even when rubbed by hand, and the usability is good.

Furthermore, the present invention is an epoch-making method for preventing variations in performance and troubles caused by blending two types of resins with low compatibility. can get.

(Examples) The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

In addition, each measurement method in this example is shown below.

(1) Apparent viscosity; according to JIS K7210.

(2) Film surface temperature: Thermocouple (C- made by Anritsu Keiki Co., Ltd.) with a thickness of about 1 mm in diameter and an exposed part of about 15 mm in length.
Using a surface thermometer connected to a 505 thermocouple (0 to 100Ω), the tip of the thermocouple was brought into contact with the film surface, and the reading after 30 seconds was taken as the film surface temperature. If the radiation from the heat source is strong, cover the side of the thermocouple that does not touch the film with aluminum foil to avoid the effects.

(3) Moisture permeability: Conforms to JIS Z0208.

(4) Hand-kneading test: A sample was cut into a predetermined size, and the samples were hand-kneaded 10 times on black paper at a distance of approximately 1 cm to compare the amount of powder that fell off.

(5) Water pressure resistance: Conforms to the clean water pressure method of JIS L1092.

Example 1 Linear low density polyethylene (temperature 200℃ shear stress
Apparent viscosity at 4.5×10 ⁵ dyne/cm ² 2.7×
10 ⁴ poise) and 40 parts by weight of high-impact polystyrene (apparent viscosity 1.5 x 10 ⁵ poise under the same conditions) were dry blended and extruded at 160 to 220°C using a T-die extrusion film forming device. It was filmed. At that time, the resin temperature immediately after exiting the die was 200°C.

The obtained film with a thickness of 110 μm was longitudinally uniaxially stretched about 9 times using a roll stretching machine with a roll surface temperature of 88° C. to obtain a porous white film with a thickness of about 30 μm. At this time, the maximum surface temperature of the film in the stretched part was 86°C.

When we measured the moisture permeability and water pressure resistance of this film, it was 3010g/m ² 24h, 176cmAq,
In the hand kneading test, no powder was observed to fall off.

Example 2 The linear low-density polyethylene, high-impact polystyrene and polybutene-1 used in Example 1 (200°C,
Apparent viscosity 1.7× under 4.5×10 ⁵ dyne/cm ²
The same procedure as in Example 1 was used except that 50, 40, and 10 parts by weight of 10 ⁴ poise) were used, respectively.
A 40μ porous white film was obtained.

In this case, the addition of polybutene-1 has the effect of lowering the apparent viscosity of polyethylene, which is the matrix phase, and increases the apparent viscosity difference with polystyrene, thereby suppressing deformation of polystyrene.

The obtained film has a moisture permeability and water pressure resistance of 3800
g/m ² for 24 hours and 158 cmAq, and no powder fell off in the hand kneading test.

By adding polybutene-1, a film with a soft texture and no stretching unevenness was obtained.

Example 3 and Comparative Example 1 Linear low-density polyethylene, high-impact polystyrene (apparent viscosity 2.3×10 ⁵ poise at 200°C, 4.5×10 ⁵ dyne/cm ² ), hydrogenated liquid polyethylene used in Examples A mixture of 60, 35, and 5 parts by weight of isoprene rubber was used to form a film by extrusion at 160 to 220°C using a circular die extrusion film forming apparatus. At that time, the resin temperature immediately after exiting the die was 190°C.

The obtained film having a thickness of 180 μm was subjected to simultaneous biaxial stretching using the tubular method so that the film was 3 times the length in the length and 3 times the width in the width using a tubular stretching device. The maximum temperature on the film surface in the stretching zone at this time was 89°C.

The resulting porous white film with a thickness of about 40 μm had a moisture permeability and water pressure resistance of 4400 g/m ² for 24 hours and 127 cmAq.

In addition, the maximum temperature of the film surface in the stretching zone is 115
℃ film was not a white film, but was translucent, and had a moisture permeability of only 35 g/m ² for 24 hours.

Comparative Example 2 The same procedure as in Example 1 was used except that a resin containing 45 and 55 parts by weight of the linear low-density polyethylene and calcium carbonate (particle size 1.8 μ) used in Example 1 was used, respectively, to a thickness of about 40 μ. A porous white film was obtained.

During this uniaxial stretching, the stretching process could not be continued stably due to the addition of a large amount of calcium carbonate fine particles.

Also, the moisture permeability of the obtained film is 2100g/m ²
Although the temperature was 24 hours, as a result of the manual rubbing test, it was observed that calcium carbonate fine particles had fallen off.

Comparative Example 3 A film was formed under exactly the same conditions as in Example 1, except that the resin added was 40 parts by weight of impact-resistant polystyrene (apparent viscosity under the same conditions: 0.5×10 ⁴ poise).
A stretched film with a thickness of about 35 μm was obtained by stretching.

The moisture permeability and water pressure resistance of this film are each 36
g/m ² for 24 hours and 200 cmAq or more, and the moisture permeability was extremely low.

Observation of the cross-sectional layer of this film revealed that the polystyrene was scaly, with almost no through holes between the front and back surfaces, and the holes had many elongated closed cells arranged in layers in the stretching direction.

Comparative example 4 High pressure normal low density polyethylene (temperature 200℃,
The apparent viscosity at a shear stress of 4.5×10 ⁵ dyne/cm ² is
60 parts by weight of crystalline nylon-6 (melting point 224℃, viscosity at 30℃ ^0.4 ×
10 ⁴ poise) 40 parts by weight were dry blended and heated to 240℃.
The resin temperature is 200℃ immediately after exiting the die.
A film was formed by extrusion so that the following was obtained.

The obtained film with a thickness of 110 μm was longitudinally uniaxially stretched about 9 times using a roll stretching machine with a roll surface temperature of 88° C. to obtain a porous film with a thickness of about 22 μm. At this time, the maximum temperature on the film surface in the stretching section was 82°C.

The water permeability and water resistance of this stretched film are
The water pressure resistance was 2400 g/m ² for 24 hours and 26 cmAq, and the water pressure resistance was poor.

Claims (1)

[Claims] 1. A polyolefin resin (A) and a thermoplastic resin (B) with low compatibility with the polyolefin resin (B) as essential components, at a temperature of 200°C and a shear stress of 4.5×10 ⁵ dyne/
The ratio of apparent viscosity measured under the condition of cm ² is B/A = 2 ~
100, and (B) 10 to 100 per 100 parts by weight of (A)
Parts by weight are melt-kneaded to form a film under conditions where the resin temperature immediately after exiting the die is 220°C or lower, and the cooled unstretched film is melt-kneaded under conditions where the maximum surface temperature of the film in the stretching zone is 30 to 110°C. A method for producing a moisture-permeable film having waterproof properties, characterized by stretching the film 1.2 to 10 times in a uniaxial direction. 2. Claims characterized in that the polyolefin resin is one or a mixture of two or more selected from the group consisting of linear low-density polyethylene, high-pressure low-density polyethylene, high-density polyethylene, and polypropylene. 2. A method for producing a moisture permeable film according to item 1. 3 Thermoplastic resins with low compatibility with polyolefin resins include polystyrene and acrylonitrile.
Claim 1, characterized in that it is one or a mixture of two or more selected from the group consisting of styrene copolymer, butadiene-styrene copolymer, and acrylonitrile-butadiene-styrene copolymer. A method for producing a moisture permeable film. 4 In addition to the essential components consisting of a polyolefin resin and a thermoplastic resin with low compatibility with the polyolefin resin, liquid polybutadiene, liquid polybutene, liquid polyisoprene, derivatives thereof, polybutene-1, and ethylene-propylene-diene ternary compounds are added. Copolymer, ethylene-propylene random copolymer, ethylene-butene random copolymer, polybutadiene resin, ethylene-vinyl acetate copolymer, one or more selected from the group consisting of 100 weight polyolefin resin. For the department,
The method for producing a moisture permeable film according to claim 1, characterized in that a total of 55 parts by weight or less is added. 5 The essential components are a polyolefin resin (A) and a thermoplastic resin (B) with low compatibility with the polyolefin resin, at a temperature of 200°C and a shear stress of 4.5×10 ⁵ dyne/
The ratio of apparent viscosity measured under the condition of cm ² is B/A = 2 ~
100, and (B) 10 to 100 per 100 parts by weight of (A)
A moisture-permeable film obtained by melt-kneading parts by weight, forming a film, and stretching the film, which has a moisture permeability of 1000 g/m ² for 24 hours, a pressure resistance of at least 50 cmAq, and a water pressure resistance of 50 cmAq or more.