JPH10139953A - Resin composition for stretchable film, and film made therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin compsn. for stretchable films which is recyclable, does not generate a harmful substance, is incinerable and stretchable, and is used for gatherings of disposable paper diapers. SOLUTION: This compsn. contains (a) 40-80% low-density polyethylene having a density of 0.86-0.90g/cm<3> , a melt index of 0.1-50g/10min, a ratio of wt. average mol.wt. to number average mol.wt. of 1.8-2.8, and a content of 4-8C α-olefin comonomer units of 18% or higher, (b) 10-50% thermoplastic elastomer comprising a polyolefinic elastomer or a polystyrenic elastomer and having a solubility parameter different from that of the low-density polyethylene, and (c) 5-20% polyethylene having a density of 0.915-0.950g/cm<3> , and 5-40 pts. inorg. filler for 100 pts. of the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition and a film for a stretch film, and more particularly to a resin composition and a film for a gather member of a disposable diaper or the like.

[0002]

2. Description of the Related Art Gather members such as disposable diapers for baby and adults, napkins with gathers, and the like are required to have elasticity. The thing which was pasted is used.

However, polyurethane foams have problems such as low strength and high price. Polyurethane films have too high stretching strength, poor hot-melt adhesiveness, are easy to block, and are difficult to release. There are problems such as necessity of use. Although natural rubber has an advantage in price, it has problems in hot melt adhesiveness, thermal adhesiveness and the like. Further, as a drawback common to these elastic members,
There is a major problem that it cannot be recycled and cannot be incinerated due to the generation of harmful substances.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a resin composition for a film and a film for use as a gather member in a stretchable disposable disposable diaper or the like which is recyclable and can be incinerated without generating harmful substances. The purpose is to provide.

[0005]

The present inventors have focused on polyolefin elastomers as materials that can be recycled and incinerated. One of them is a copolymer of ethylene and α-olefin, A study was conducted on the applicability of low-density polyethylene, which is characterized by a narrow molecular weight distribution and low crystallinity, to the gather member.

The low-density polyethylene alone could not be formed because the film was sticky and could not be formed. However, by adding a specific elastomer having a solubility parameter different from that of the low-density polyethylene to the low-density polyethylene, the film became opaque. In addition, moderate surface roughness occurs on the surface, film formation becomes possible, and by further adding polyethylene and an inorganic filler, film forming properties are improved, and blocking is difficult, and the obtained film is required as the above member. The present inventors have found that the above physical properties can be satisfied and completed the present invention.

That is, according to the present invention, (a) the density is 0.8
6 to 0.90 g / cm ³ , melt index 0.1
Low-density polyethylene having a weight-average molecular weight / number-average molecular weight of 1.8 to 2.8 and a carbon number of 4 to 8 and containing at least 18% by weight of a low-density polyethylene of 40 to 80%. %, (B) selected from polyolefin-based elastomers and polystyrene-based elastomers,
Composition 100 comprising 10 to 50% by weight of a thermoplastic elastomer having a solubility parameter different from that of low density polyethylene (a) and (c) 5 to 20% by weight of polyethylene having a density of 0.915 to 0.950 g / cm ^3. The gist of the present invention is a resin composition for a stretch film, which comprises 5 parts by weight and (d) 5 to 40 parts by weight of an inorganic filler.

The composition of the present invention is characterized in that the α-olefin comonomer is 1-octene and the content thereof is 20 to 35% by weight.

In the composition of the present invention, the solubility parameter of the thermoplastic elastomer (b) is larger than the solubility parameter of the low-density polyethylene (a), and the range is 8.0 to 11.0. It is characterized by.

The composition of the present invention is characterized in that the thermoplastic elastomer (b) is an ethylene-vinyl acetate copolymer.

Further, the present invention provides a film obtained by molding the above composition.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition for stretchable films of the present invention comprises (a) a density of 0.86 to 0.90 g / cm ³ , a melt index of 0.1 to 50 g / 10 min, and a weight average molecular weight / A low-density polyethylene having a number-average molecular weight of 1.8 to 2.8 and an α-olefin comonomer having 4 to 8 carbon atoms in an amount of 18% by weight or more, 40 to 80% by weight;
(B) low-density polyethylene selected from polyolefin-based elastomers and polystyrene-based elastomers (a)
Thermoplastic elastomer 1 having different solubility parameter from
0-50% by weight and c) a density of 0.915-0.950
The composition contains 100 parts by weight of a composition containing 5 to 20% by weight of g / cm ³ of polyethylene and (d) 5 to 40 parts by weight of an inorganic filler.

The low-density polyethylene of the component (a) has a density of 0.86 to 0.90 g / cm ³ , a melt index of 0.1 to 50 g / 10 min, and a weight-average molecular weight / number-average molecular weight of 1.8 to 1.8. 2.8 and α- having 4 to 8 carbon atoms.
It contains 18% by weight or more of an olefin comonomer. Among the above α-olefin comonomers, 1-
Octene is desirable, and its content is preferably 20 to 35% by weight, particularly preferably 22 to 30% by weight. If the content of the α-olefin comonomer is less than 18% by weight, sufficient flexibility cannot be obtained. The component (a) has a melt index (MI: 190 ° C, load 2.16 kg) of 0.1 to 0.1.
50 g / 10 min, preferably 0.5 to 20 g / 10 min is used. If the MI is less than 0.1 g / 10 minutes,
When the film is formed, the torque increases and extreme melt fracture occurs. When the melt exceeds 50 g / 10 minutes, bubbles become unstable and the film formation stability deteriorates.

The linear low-density polyethylene of the component (a) is characterized in that the weight average molecular weight / number average molecular weight (Mw / Mn), which is a measure of the molecular weight distribution, is as small as 1.8 to 2.8. Such a polyethylene is preferably produced using a metallocene catalyst capable of narrowing the width of the molecular weight distribution.

The metallocene catalyst is a compound having a structure in which a transition metal such as titanium, zirconium or hafnium is sandwiched by an unsaturated cyclic compound containing a π-electron cyclopentadienyl group or a substituted cyclopentadienyl group. It is a combination of a metallocene and a promoter such as an aluminum compound.

Component (a) is prepared by reacting a metallocene such as titanocene or zirconocene with a metallocene catalyst obtained by activating a metallocene such as an alkylaluminoxane, an alkylaluminum, an aluminum halide or an alkylaluminum halide as a cocatalyst. And an α-olefin having 4 to 8 carbon atoms of a comonomer,
Preferably 1-butene, 1-pentene, 1-hexene,
It can be produced by solution polymerization of 4-methyl-1-pentene, 1-heptene, 1-octene and the like, particularly preferably 1-octene.

The component (b) is a thermoplastic elastomer selected from a polyolefin elastomer and a polystyrene elastomer. Examples of the polyolefin-based elastomer include an ethylene-vinyl acetate copolymer, an ethylene-propylene copolymer, an ethylene-propylene-diene copolymer and the like, all of which show elastomeric properties. Examples of the diene compound in the ethylene-propylene-diene copolymer include ethylidene norbornene, 1,4-hexadiene, dicyclopentadiene, and the like.

The ethylene-vinyl acetate copolymer has a vinyl acetate content of usually 10 to 40% by weight. The ethylene-propylene copolymer has a propylene content of usually 3
0 to 70% by weight. The ethylene-propylene-diene copolymer usually has an ethylene content of 40 to 65% by weight, a propylene content of usually 25 to 55% by weight, and a diene content of 1 to 15% by weight.

Among the above-mentioned polyolefin-based elastomers, ethylene-vinyl acetate copolymers are desirable. Particularly, the content of vinyl acetate is 15 to 30% by weight, and the melt flow rate (MFR: 190 ° C., load: 2.16 kgf / cm)
² ) is preferably an ethylene-vinyl acetate copolymer of 0.8 to 25 g / 10 min.

Examples of the polystyrene-based elastomer include a block copolymer of a polymer block mainly composed of styrene and a polymer block mainly composed of butadiene or isoprene, and a hydrogenated product of this block copolymer. Specific examples thereof include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and styrene-ethylene-butene-styrene block copolymer which is a hydrogenated product of SBS. (SEBS), styrene hydrogenated styrene-ethylene-propylene-styrene block copolymer (SEPS), and the like. These block copolymers preferably have a styrene polymer block content of 30% by weight or less.
If it exceeds 30% by weight, the resulting film is hard and the distortion is undesirably large.

The thermoplastic elastomer selected from the polyolefin elastomer and the polystyrene elastomer of the component (b) needs to have a solubility parameter (SP value) different from that of the component (a).
It is preferable that the P value is larger than that of the component (a) and the range is 8.0 to 11.0.

The SP value is calculated using the following Small's equation.

SP = dΣG / M where M: unit molecular weight of polymer, d: density, G: constants specific to atomic groups and groups The polyethylene of component (c) used in the present invention has a density of 0. 915 to 0.950 g / c
m ³ , preferably a melt index (M
I: 190 ° C, load 2.16 kgf) 0.5 to 10 g
/ 10 minutes. Polyethylene having such a density includes low-density polyethylene having a density of 0.925 g / cm ³ or less, obtained by a high-pressure method, and copolymerization with a trace amount of an α-olefin such as 1-butene in the presence of a Ziegler catalyst. Is 0.920 to 0.930 g / cm ³
And low-density polyethylene (L-LDPE) and medium-density polyethylene having a density of 0.926 to 0.940 g / cm ^3. Of these, low-density polyethylene obtained by a high-pressure method is particularly desirable.

Examples of the inorganic filler of the component (d) include talc, calcium carbonate, zeolite, gypsum, carbon black, mica, clay, kaolin, silica, and diatomaceous earth. Of these, talc and calcium carbonate are particularly preferred. These inorganic fillers are desirably in the form of particles having an average particle diameter of 0.5 to 5 μm, and those whose surface is treated with a surface treating agent such as a fatty acid can also be used.

The resin composition for a stretch film of the present invention comprises:
Component (a) is 40 to 80% by weight, component (b) is 10 to 5% by weight.
100 parts by weight of a composition containing 0% by weight and 5 to 20% by weight of the component (c) and 5 to 40 parts by weight of an inorganic filler (d).

When the component (a) is less than 40% by weight, the flexibility of the film is insufficient, and when it exceeds 80% by weight, the opening property and the film forming stability at the time of film formation by the inflation method are deteriorated. If the component (b) is less than 10% by weight, the torque at the time of film formation is large and melt fracture occurs. If it exceeds 50% by weight, pinholes and the like are generated at the time of film formation, making film formation difficult. If the component (c) is less than 5% by weight, the stability of bubbles at the time of film formation by the inflation method deteriorates, and
If it exceeds 0% by weight, the film is stretched (100%
(During elongation) increases. Further, per 100 parts by weight of the composition containing the components (a), (b) and (c),
When the amount of the component (d) is less than 5 parts by weight, the opening property and the blocking resistance are deteriorated.

The composition of the present invention may optionally contain other components such as an antioxidant, an ultraviolet absorber and a coloring agent in addition to the components (a), (b), (c) and (d). can do.

The composition of the present invention is prepared by adding the components (a), (b), (c), (d) and, if necessary, other components, and using, for example, a Henschel mixer or a high-speed mixer. After dry blending in advance, for example,
It is obtained by melting and kneading using an extruder or the like under heating at about 230 ° C., extruding, and pelletizing.

The present invention further provides a film obtained by molding the above resin composition for an elastic film. As a method of molding the composition into a film, a flat film can be molded by a T-die extruder which is a usual plastic molding method. Considering high-speed moldability (improvement in productivity) and the like, an air-cooled inflation molding method for forming a tubular film is preferable. The air-cooled inflation molding method is desirably performed at a resin temperature of 150 to 180 ° C. and a blow ratio of 2.0 to 5.0.

The thickness of the film is appropriately selected depending on various uses, but is usually preferably 150 μm or less.
A more preferable film thickness is 20 to 60 μm.
When the thickness of the film exceeds 150 μm, the film having a width of 30 mm or more is not preferable because the film becomes hard. In the above-described film forming method, a film is formed by, for example, an air-cooled inflation film forming apparatus, and slit into a predetermined width to obtain a sheet-shaped or tape-shaped wound product. Further, the stretching may be performed.

Further, a tape obtained by applying a hot melt adhesive or the like to the slit stretchable film is adhered to a non-woven fabric, a woven fabric, a plastic film or a sheet, and a laminate thereof in a stretched state. By reducing the expansion and contraction of the diaper, for example, a gather member such as a diaper can be formed.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.

The components used in preparing the composition of the present invention, the evaluation of film-forming stability and the method of measuring the physical properties of the obtained film are as follows.

Each component (a) used in preparing the composition : Component (a) -1: low-density polyethylene manufactured by using a metallocene catalyst (trade name Engage E manufactured by Dow Chemical Company)
G8200; MI 4.6 g / 10 min, density 0.871 g
/ Cm ³ , Mw / Mn 1.96, SP value 7.8) (a) -2: Low density polyethylene (manufactured by Dow Chemical Company, trade name Engage E) using a metallocene catalyst
G8150; MI 0.5 g / 10 min, density 0.868 g
/ Cm ³ , Mw / Mn 2.15, SP value 7.8) (b) Component (b) -1: Ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar Co., Ltd., trade name NUC3195; MFR 5.0 g)
/ 10 min, density 0.95 g / cm ³ , vinyl acetate content 25% by weight, SP value 10.0) (b) -2: ethylene-vinyl acetate copolymer (trade name DQDJ3269, manufactured by Nippon Unicar Co., Ltd.) ; MFR 20g
/ 10 min, density 0.95 g / cm ³ , vinyl acetate content 28% by weight, SP value 10.0) (b) -3: Styrene-butadiene-styrene block copolymer (Texa Copolymers Co., Ltd., trade name Vector) 8550D; styrene polymer block content 30% by weight, MFR 8.0 g / 10 min. 200 ° C., load 5 kg
f, density 0.94 g / cm ³ , SP value 8.4) (C) component (C) -1: high-pressure low-density polyethylene (manufactured by Nippon Unicar Co., Ltd., trade name NUC8506; MI 0.8 g / 10)
Min, density of 0.922 g / cm ³⁾ (d) component (d) -1: Talc (Hayashi Kasei Co., Ltd., trade name Micron White 500S; average particle size 2.6 [mu] m) (d) -2: Calcium carbonate (Shiraishi Calcium Co., Ltd.
Made, trade name PO filler 150B; average particle size 2.2μ
m) Evaluation of film formation stability A film was formed by the inflation method of Example 1 and evaluated according to the following criteria.

A: Very stable film formation without bubble sway, distortion and wrinkles.

：: The bubble was slightly swayed, but the film could be formed almost stably.

X: Film formation was not possible.

Method for measuring physical properties of film : Strength at 50% elongation: Measured according to JIS L1096 using the following equipment and conditions.

Equipment used: Strograph W (manufactured by Toyo Seiki Co., Ltd.) Measurement sample size: 25 mm × 150 mm Chuck interval: 100 mm Tensile speed: 300 mm / min Measurement atmosphere: 23 ° C., 50% RH 100% elongation strength: JIS According to L1096,
The measurement was performed under the same conditions. Strength at break: JIS L1
The measurement was carried out according to the following instruments and conditions in accordance with No. 096.
Equipment used: Strograph W (manufactured by Toyo Seiki Co., Ltd.) Measurement sample size: 25 mm × 150 mm Chuck interval: 50 mm Tensile speed: 300 mm / min Measurement atmosphere: 23 ° C., 50% RH Elongation at break: Based on JIS L1096 , And under the same conditions.

One-cycle strain after 100% elongation: J
The measurement was carried out under the same conditions as those in accordance with IS L1096.

The above items (1) to (4) were measured in the machine direction (MD) of the film.

Opening property: A relatively outside portion of the raw film wound on a paper tube is cut in a transverse direction (TD) by a cutter, and the inner surfaces of the inflation tube are pulled in a 180 ° direction, and the peel strength is measured according to JIS. The measurement was performed three times under the following conditions in accordance with L1096, and the average value was used as a measure of openness.

Equipment used: Strograph W (manufactured by Toyo Seiki Co., Ltd.) Specimen size: 55 mm × 200 mm Chuck interval: 50 mm Tensile speed: 300 mm / min Measurement atmosphere: 23 ° C., 50% RH Blocking degree: wound around a paper tube A relatively outer portion of the blown film taken is laterally (T)
D) was cut into a flat film. The laminate of this sheet was cut into a size of 55 mm × 200 mm to obtain a sample for measuring the degree of blocking.

Next, a copy sheet having a thickness of 90 μm was placed on a glass plate having a size of 200 mm × 300 mm. Twenty samples were placed on the copy sheet, and then 180 mm × 200 mm was placed thereon. Place a glass plate weighing 830 g and a weight of 5 kg on a size of × 8 mm.
Stored in a gear oven at 0 ° C. for 7 days, measured 180 ° peel strength between samples after storage by the same method as above,
The value was used as a measure of the degree of blocking.

Example 1 64 parts by weight of (a) -1 component, 27 parts by weight of (b) -1 component, 9 parts by weight of (c) -1 component and 15 parts by weight of (d) -1 component (Model SF, manufactured by Kawata Corporation)
C-50), followed by melt-kneading at 170 ° C. using a twin-screw kneading extruder (Model TEX-30, manufactured by Nippon Steel Works, Ltd.), and pellets comprising the composition of the present invention. I got

Using the obtained composition, a film having a thickness of 50 μm and a folding width of 410 mm was manufactured under the condition of a blow-up ratio of 2.6 by an air-cooled inflation film forming apparatus. After winding, a film of the present invention was obtained. The bubble was stable during film formation. The physical properties of the obtained film were measured in accordance with the above test methods, and the results are shown in Table 2.

(Examples 2 to 5) (a) -1 component, (b) -1 component and / or (d) -1
The components were changed to the components shown in Table 1 and their blending ratios were shown in Table 1.
A composition was obtained in the same manner as in Example 1, except for the following. Using the obtained composition, films having the thicknesses shown in Table 2 were obtained in the same manner as in Example 1, and the physical properties of those films were measured. The results are shown in Table 2.

Comparative Example 1 A film was produced in the same manner as in Example 1 using only the component (a) -1, but could not be made into a film.

Comparative Example 2 A composition was obtained in the same manner as in Example 1 except that the component (b) -1 was not used. Using the obtained composition, a film was obtained in the same manner as in Example 1, and the physical properties of the film were measured. The results are shown in Table 2.

[0050]

[Table 1]

[Table 2] As is clear from Table 2, the film formed from the composition of the present invention satisfies the required elongation strength, strain and rupture strength, and elongation of the stretchable film, and can be stably formed. The peel strength (opening property) and the degree of blocking are small, and the film can be easily formed.

[0051]

EFFECT OF THE INVENTION By using the composition of the present invention, a stretchable film can be stably formed, and
Blocking is difficult, and the opening property of the tube during film formation can be improved. Also, the obtained elastic film is
Maintains physical properties required for members such as gathers of disposable diapers. Further, the composition and the film of the present invention include:
Since it is made of a polyolefin-based polymer, it can be recycled and can be incinerated without generating harmful substances.

Claims (5)

[Claims] (1) a density of 0.86 to 0.90 g / c
m ³ , melt index is 0.1 to 50 g / 10 minutes,
Weight average molecular weight / number average molecular weight is 1.8 to 2.8, and 1 to 4 carbon atoms of an α-olefin comonomer
40 to 80% by weight of low-density polyethylene containing 8% by weight or more, (b) a thermoplastic elastomer selected from polyolefin-based elastomers and polystyrene-based elastomers and having a solubility parameter different from that of low-density polyethylene (a) 10 to 50% by weight And (c) a density of 0.915 or more
100 parts by weight of a composition containing 5 to 20% by weight of 0.950 g / cm ³ of polyethylene and (d) inorganic filler 5
A resin composition for a stretchable film, comprising from about 40 parts by weight. 2. The resin composition for an elastic film according to claim 1, wherein the α-olefin comonomer is 1-octene and the content thereof is 20 to 35% by weight. 3. The method according to claim 1, wherein the solubility parameter of the thermoplastic elastomer (b) is larger than the solubility parameter of the low-density polyethylene (a), and the range is 8.0 to 11.0. Or the resin composition for stretch films according to claim 2. 4. The resin composition for a stretch film according to claim 1, wherein the polyolefin-based elastomer is an ethylene-vinyl acetate copolymer. 5. A film formed by molding the resin composition for an elastic film according to claim 1.