JPH0353931A - Multi-layer and porous film and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a film superior in moisture permeability and gas permeability where sealing strength is improved with a film layer having the low melting point and a deformation of the film to be generated with sealing is prevented with a film layer having the high melding point, by providing film layers whose melting points are different from each other as a multi-layer and porous film. CONSTITUTION:A porous film comprised by orienting after film making by compounding a filling agent to thermoplastic resin/for melting is constituted of a resin composition of a layer (a) (a layer comprised of 80-250 pts.wt. filling agent on the basis of 100 pts.wt. polyolefin resin) and a layer (b) (a layer comprised of 100-900 pts.wt. filling agent on the basis of 100 pts.wt. thermoplastic resin and having the melting point falling within a range of an least 60 deg.C and not exceeding the Vicat softening point of the polyolefin resin of the layer (a)). Then the layer (b) is formed on one side or both sides of the layer (a) so that a thickness ratio (a/b) after orientation of the layers (a), (b) becomes 0.35-25. For example, high-density polyethylene and/or linear low-density polyethylene is used for the polyolefin resin of the layer (a). For example, ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer is used for the thermoplastic resin of the layer (b).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer porous film with excellent thermal adhesiveness and a method for producing the same.

More specifically, it consists of a (al layer) made of a polyolefin resin and a filler, and a thermoplastic resin (made of a filler) whose melting point is 60 ° C. or higher and (a layer that is below the Vicat softening point of the polyolefin resin of the aJ layer). The present invention relates to a multilayer porous film having a multilayer structure of one or more layers, in which the middle layer (b) is formed on one or both sides of the (a) layer, and a method for producing the same.

As mentioned above, the porous film of the present invention forms a multilayer structure by using resins with different thermal behavior in the (a) layer and (bJ layer), and is useful for waterproof clothing, disposable diapers, and sanitary materials. It can be used for leakage materials, etc., but especially,
Ideal for heat-sealing and composite applications.

[Conventional technology]

Conventionally, various methods have been proposed to obtain porous films by blending organic or inorganic incompatible substances with polyolefin resins, melting them, and then stretching them. For example, JP-A-60-129246 discloses In the publication, a polyolefin resin and halium sulfate are blended in a specific ratio, and in JP-A-57-47334, a polyolefin resin, a filler, and liquid polybutadiene are blended in a specific ratio, and after melt-forming, stretching is performed to form a porous film. It shows how to get the film.

The porous film obtained by the above method has characteristics such as moisture permeability and air permeability while having a waterproof function, so it can be used for waterproof clothing such as rain gear, disposable diapers, leak-proof films for sanitary materials, packaging materials, batteries, etc. Applications include separators, iIta materials, etc.

These porous films are used in a wide range of applications, either by adhering the film itself or by adhering it to another plastic film or paper, as a binding material for packaging materials such as desiccant or vegetable packaging.

Examples of the bonding method include a method of applying an adhesive, a heat sealing method, and the like.

However, when applying adhesive to the entire surface, moisture permeability and air permeability are impaired, so it is impossible to heat seal the entire surface, and it is only applied partially, which increases the manufacturing process. However, it has disadvantages such as high cost.

In addition, in the case of the heat-sealing method, the cost is lower than applying adhesive, but since the porous film is stretched, the heat-sealed part is likely to shrink, causing wrinkles or extreme cases. In this case, only the seal portion shrinks, causing problems such as a complete loss of flatness and the formation of bottle holes. Further, there are problems in that the molecular chains become misoriented during sealing, resulting in a significant decrease in strength.

[Problem to be solved by the invention]

The problem of the present invention is that there is no need to apply an adhesive to a porous film obtained by blending a filler with a polyolefin resin, and that there is no deformation of the sealed portion by using a thermal adhesion method such as heat sealing. An object of the present invention is to provide a multilayer porous film having excellent sealing strength, moisture permeability, and air permeability, and a method for producing the same.

[Means to solve the problem]

In order to solve the above problems, the present inventors have made extensive studies,
We have finally arrived at the present invention.

That is, the present invention provides a porous film formed by blending a filler into a thermoplastic resin, melting it, and then stretching it, wherein the porous film contains the resins of the (a) layer and (b) layer shown below. &l'I, and the thickness ratio (a/b) of the (a) layer and (b) layer after stretching is 0.35 to 25.
(A multilayer porous film characterized by forming the (b) layer on one or both sides of the aJ layer, and a method for producing the same.)

(a) Layer: A layer consisting of 80 to 250 parts by weight of filler based on 100 parts by weight of polyolefin resin.

7 (bJ layer: a layer consisting of 100 to 900 parts by weight of a filler with respect to 100 parts by weight of a thermoplastic resin whose melting point is 60° C. or higher and below the softening point of the polyolefin resin of the Al layer.

Here, the thickness ratio of the (a) layer and (b) layer after stretching in the present invention will be explained in detail.

The true density of the film obtained in the present invention is ρ. g/cc, (
a) The density of the polyolefin resin of the layer is m, g/cc,
The density of the filler is n. g/cc, and the amount of filler added is Wa parts by weight based on 100 parts by weight of resin.

Similarly, the density of the thermoplastic synthetic resin of layer (b) is set to m, g/
cc, the density of the filler is nbg/cc, and the amount of filler added is W, parts by weight per 100 parts by weight of the resin.

(a) The true density ρ, g/cc of the layer is 1004-w, (b) The true density of the layer ρag/cc is 100 +W+, 8 becomes.

The multilayer porous film has n layers, (a) layer is A layer, (bJ
When the layer is B layer (n = A + B), the (a) layer is X%, the (b) layer is y%, and (aJ layer and (b
) If each layer has the same thickness, the thickness ratio 2 per layer is z-(x/A)/(y/B)=. −=
(3) becomes.

x 1y= 1 0 0 - (4
), and the true density of the film is 1 0 0 Therefore, if x and y are determined from the above equations (1) to (5), the thickness ratio will be (ρ0-ρ3)/B.

The thickness ratio (a/b) of the multilayer porous film of the present invention is in the range of 0.35 to 25 by the above method.

The present invention will be explained in detail below.

As the layer (a) in the present invention, it is possible to use a Juhoku composition formed by blending 80 to 250 parts by weight of a filler with an average particle size of 0.1 to 30 μm to 100 parts by weight of a polyolefin resin. can.

The polyolefin resin in the present invention includes, for example, low density polyethylene (LDIIE), high density polyethylene (
lIDI'E), linear low density polyethylene (L-LDP
IE), homopolymers of propylene (PP), homopolymers of butene, etc., copolymers such as ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-vinyl acetate copolymers, etc., or their blen 1 ′.

Linear low density polyethylene is a copolymer of ethylene and α-olefin, and the α-olefins include butene-1 hexene-1, octene-1, 4-methylpentene-1, decene-1, dodecene-1 etc. can be used.

Among the above polyolefin resins, polypropylene, high density polyethylene, and linear low density polyethylene are particularly preferred.

Note that heat stabilizers, ultraviolet stabilizers, antistatic agents, pigments, fluorescent agents, etc. may be added to the polyolefin resin according to conventional methods.

In the present invention, inorganic and organic fillers are used in the (a) layer and (bJ layer), and the inorganic fillers include calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, and carbonic acid. Magnesium, halium carbonate, magnesium sulfate, halium sulfate, calcium sulfate,
aluminum hydroxide, zinc oxide, magnesium hydroxide,
Calcium oxide, magnesium oxide, titanium oxide, alumina, mica, calcium silicate, glass powder, shirasu balloon, zeolite, clay silicate, etc. are used, and barium sulfate, calcium carbonate, zinc oxide, silica, magnesium hydroxide, etc. are particularly suitable. It is.

In addition, fatty acids or their metal salts, silicon,
Surface treatment with silane, resin acid, etc. is preferable in order to further enhance dispersibility in the resin and improve stretchability.

Further, examples of the organic filler include wood flour, pulp, meladan powder, silicone resin powder, and the like.

1. (The average particle size of the filler used in the Al layer is from Ol to 3.
0 μm, preferably 0.3-2.5 μm,
Appropriate.

If the average particle size is less than 0.1 μm, the filler is likely to undergo secondary aggregation and will not be sufficiently dispersed in the resin, resulting in lumps or stretch breakage.

On the other hand, if it exceeds 3.0 μm, the stretchability is poor and the stretching may break, and the pore diameter becomes large, resulting in a poor function as a porous film.

The amount of the filler added to the layer (a) is 80 to 250 parts by weight per 100 parts by weight of the polyolefin resin.

If the amount of filler is less than 80 ffi parts, sufficient air permeability cannot be obtained because the porosity is not sufficiently made and there are few communicating pores.
If the amount exceeds 250 parts by weight, the shape and stretchability of the sheet-like product will deteriorate.

The thermoplastic synthetic resin of the (+) layer in the present invention is not particularly limited as long as its melting point is 60° C. or higher and is lower than or equal to the vicant softening point of the polyolefin resin of the aJ layer.

For example, polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylic acid copolymer (EAA),
), ionomer resins, polyacid resins, polyester resins, polyurethane resins, and the like.

Particularly preferred are ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and low-melting polyamide.

The average particle size of the filler used in layer (b) is between 0.1 and 8.
．． 0 μm, preferably 0.7-5. OtIm's is suitable.

If the average particle size is less than 0.1 μm, the filler is likely to undergo secondary aggregation and will not be sufficiently dispersed in the resin, resulting in lumps and, as a result, stretching breakage.

On the other hand, if it exceeds 8.0 μm, the stretchability is poor and the stretching may break, and the pore diameter becomes large, resulting in a poor function as a porous film.

Also, the average particle size of the filler used in (b) N is (a
) is preferably larger than that of the filler used in the layer.

The (l)) layer has poor stretchability compared to the (al) layer, impairing the moisture permeability of the (a) layer, but increasing the particle size of the filler is effective in preventing this.

The amount of the filler added to the layer (b) is 100 to 900 parts by weight, preferably 150 to 800 parts by weight, per 100 parts by weight of the polyolefin resin.

If the amount of the filler is less than 100 parts by weight, sufficient air permeability cannot be obtained due to insufficient porosity and fewer communicating pores.
If the amount exceeds 0.00 parts by weight, the forming and stretching properties of the sheet-like product will deteriorate.

In the present invention, (a) on one or both sides of the layer (b)
Provide layers.

Although it varies depending on the application, it is generally preferable to provide it on the - side of the layer (a).

Further, when provided on both sides, the layer (b) usually has the same composition on each side, but it is also possible to use layers with different composition strengths.

The thickness ratio (a/b) of the (a) layer and (bJ layer) is 0.35 ~
25, preferably 0.5 to IO.

If the thickness ratio becomes smaller than 0.35 and the thickness of the (b) layer increases, the extensibility of the (b) layer decreases and wrinkles etc. appear in the sealed portion, which is not preferable.

In addition, on the contrary, it becomes larger than 25, and (thickness of the bl layer is (a
If it is smaller than the thickness of the layer (b), the thickness of the layer (b) will be non-uniform, and the sealing strength will be uneven or lower, which is not preferable.

Next, a method for producing a porous film of the present invention will be explained.

The method for producing a multilayer porous film of the present invention, namely (
The BL layer can be provided on one or both sides of the Al layer by known methods such as coextrusion, extrusion lamination, and thermal lamination, but the method does not impair productivity, moisture permeability, or air permeability. In this case, a method by coextrusion is suitable.

(a) After blending a filler with a polyolefin resin and other additives such as a heat stabilizer, an ultraviolet stabilizer, an antistatic agent, a pigment, and a fluorescent agent as necessary, Henshi J.
Mix using a tumbler type mixer such as Super Mixer I5, and then knead using a conventional single-screw or twin-screw extruder to form pellets.

In addition, as the (b) layer, thermoplastic. Fillers and other additives such as heat stabilizers, ultraviolet stabilizers, antistatic agents, pigments, and fluorescent agents are added to the plastic resin as necessary, and pelletized using the same method as for layer (a). do.

Next, these pellets are melt-formed into a film by coextrusion using an inflation molding machine or a T-die molding machine.

At this time, it is also possible to directly shape the product using a coextruder without pelletizing it.

Then, in at least one axis, 1. 1 Stretch for 4 or more times. Stretching may be performed in multiple stages,
It may be stretched biaxially.

If the stretching ratio is less than 1.1 times, the film will not be sufficiently porous.

Further, after stretching, heat setting may be performed to increase the shape stability of the holes.

The multilayer porous film 1 obtained by the above method is 6 Heat seal the film itself or other substrates.

Other base materials include, but are not particularly limited to, thermoplastic resin films, nonwoven fabrics, paper, warifs, and the like.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

Examples 1 to 8, Comparative Examples 1 to 8 For 100 parts by weight of the thermoplastic resin shown in Table 1,
The fillers shown in Table 2 were blended in the amounts shown in Table 2, mixed using a Henschel mixer, kneaded using a twin screw extruder, and further pelletized.

The resulting pellets were simultaneously formed into films using a coextruder using the combinations of layers shown in Table 2 (Al layer), in Examples 1 to 7, one layer in Comparative Examples 1 to 7, and three layers in Example 8. After that,
Examples 1 to 8 and Comparative Examples 1 to 6 at the stretching ratio shown in Table 2.
, Comparative Example 8 was stretched at a temperature of 70°C, and Comparative Example 7 was stretched at a temperature of 40°C to obtain a multilayer porous film.

For Example 3, biaxial stretching was carried out successively by 3 times in length and then 5 times in width.

In addition, in this embodiment, the partner group {A is
After extruding the linear low-density polyethylene shown in Table 1 using a T-die extruder, it was stretched 6 times in the longitudinal direction, and the resulting film was used.

The heat sealing method of this example uses a sealer,
At the temperature shown in Table 2, the gauge pressure is 1 kg/c+fl. It took 1 second.

The following physical properties were measured for the obtained film, and the measurement results are shown in Table 2.

■Air permeability (sec/IOOcc) : Compliant with JIS-8117.

■Tensile strength (g/25mm): In accordance with JIS-8113, the strength when the sample breaks is measured in the running direction (MD) and the direction perpendicular to MD (TD).

Sample size: 100mm length x 25mm width Measurement temperature: 23±i'c ■Heat seal strength (g/15mm): Take a sample so that the width of the heat seal part is 15 mm, and place it in a Tensilon tester with a porous film. Each base material is held between chucks and pulled at a pulling speed of 200 m/min, and the strength when the seal part peels off or breaks is measured.

■Shape retention: The state of deformation, such as shrinkage of the film at the heat-sealed portion, was observed.

× 〈 ○ 〈 ◎ Deformation No deformation ■Bag breakage test: A bag of 17c+nx20cm was made from the multilayer porous film of the example and the mating substrate, and the bag filled with 500g of calcium carbonate was dropped from a height of 150cm, and the bag was broken. Measure the number of times you bag it.

〔Effect of the invention〕

By providing film layers with different melting points as a multilayer porous film, the present invention improves the sealing strength with the film layer with a low melting point, and reduces the deformation of the film caused by heat sealing with the film layer with a high melting point. It is possible to obtain a film with excellent moisture resistance, moisture permeability, and air permeability.

Sign spread flat 3 53931(7)

Claims (1)

[Claims] 1. After blending a filler with a thermoplastic resin and melting it into a film,
In the porous film formed by stretching, the porous film is composed of the resin compositions of the (a) layer and (b) layer shown below, and the thickness ratio of the (a) layer and (b) layer after stretching ( a/b
) is 0.35 to 25. A multilayer porous film characterized in that a layer (b) is formed on one or both sides of the layer (a). (a) Layer: A layer consisting of 80 to 250 parts by weight of filler based on 100 parts by weight of polyolefin resin. (b) Layer: Consisting of 100 to 900 parts by weight of a filler per 100 parts by weight of a thermoplastic synthetic resin whose melting point is 60°C or higher and below the Vicat softening point of the polyolefin resin of layer (a). layer. 2. The multilayer porous film according to claim 1, wherein the polyolefin resin of layer (a) is polyethylene and/or polypropylene. 3. The multilayer porous film according to claim 1, wherein the polyolefin resin of layer (a) is high density polyethylene and/or linear low density polyethylene. 4. The thermoplastic resin of the (b) layer is one selected from the group of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and low melting point polyamide resin, or 2. The multilayer porous film according to claim 1, which is a mixture of more than one kind. 5. In a method of manufacturing a porous film by blending a filler with a thermoplastic resin, melting it, and then stretching it, the porous film has the resin composition of the (a) layer and (b) layer shown below. (a) on one or both sides of the layer (b
) A multilayer unstretched film with layers formed thereon is melt-formed, and then stretched in at least one direction so that the thickness ratio (a/b) of the (a) layer and (b) layer after stretching is 0.35 to 25. A method for producing a multilayer porous film, which comprises stretching the film. (a) Layer: A layer consisting of 80 to 250 parts by weight of filler based on 100 parts by weight of polyolefin resin. (b) Layer: A layer consisting of 100 to 900 parts by weight of a filler per 100 parts by weight of a thermoplastic resin whose melting point is 60°C or higher and below the Vicat softening point of the polyolefin resin of layer (a). . 6. The method for producing a multilayer porous film according to claim 5, wherein the polyolefin resin of the layer (a) is polyethylene and/or polypropylene. 7. The method for producing a multilayer porous film according to claim 6, wherein the polyolefin resin of layer (a) is high density polyethylene and/or linear low density polyethylene. 8. The thermoplastic synthetic resin of layer (b) is one or two selected from the group of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and low melting point polyamide resin. The method for producing a multilayer porous film according to claim 5, wherein the method is a mixture of more than one kind.