JPH10139951A - 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 30-90% 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 and 10-70% thermoplastic elastomer comprising a polyolefin elastomer or a polystyrene elastomer and having a solubility parameter different from that of the low-density polyethylene.

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.

[0003] However, polyurethane foams have problems such as low strength and high price. Polyurethane-based films have too high stretch strength, poor hot-melt adhesiveness, are easily blocked, and are difficult to release from paper during film formation. 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. The present inventors have found that the surface has moderate surface roughness, film formation is possible, and the obtained film satisfies the physical properties required for the above-mentioned members, and the present invention has been completed.

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 α-olefin comonomer of 18% by weight or more 30 to 90% by weight %, And (b) a thermoplastic elastomer selected from a polyolefin-based elastomer and a polystyrene-based elastomer and having a solubility parameter different from that of the low-density polyethylene (a) in the range of 10 to 70% by weight. The gist is a resin composition.

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 a carbon number of 4 to 8 α-olefin comonomer of 18% by weight or more of 30 to 90% 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 to 70% by weight.

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 kgf) of 0.1.
５０50 g / 10 min, preferably 0.5 to 20 g / 10 min. If the MI is less than 0.1 g / 10 minutes, the moldability deteriorates and melt fracture occurs,
If the film skin becomes extremely bad, and if it exceeds 50 g / 10 minutes, the stability of bubbles at the time of film formation becomes poor.

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 above-mentioned metallocene catalyst is a compound having a structure in which a transition metal such as titanium, zirconium or hafnium is sandwiched between unsaturated cyclic compounds 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.

The component (a) is prepared by reacting a metallocene such as titanocene or zirconocene with a metallocene catalyst obtained by activating a cocatalyst with an aluminum compound such as an alkylaluminoxane, an alkylaluminum, an aluminum halide or an alkylaluminum halide. Α-olefin having 4 to 8 carbon atoms of the comonomer, preferably 1-butene, 1-pentene, 1-hexene,
It can be produced by solution polymerization of -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 Here, M: unit molecular weight of polymer, d: density, G: constants specific to atomic groups and groups. 90% by weight, component (b) 1
It contains 0 to 70% by weight. (A) Component is 30
If the amount is less than 10% by weight, the elasticity of the film becomes insufficient, and
If it exceeds 0% by weight, tackiness occurs in the film, and a sticky feeling occurs. If the component (b) is less than 10% by weight,
When the torque at the time of film formation increases, extreme melt fracture occurs on the film surface, and when it exceeds 70% by weight, the stability of bubbles at the time of film formation deteriorates.

In the above composition, in addition to the component (a) and the component (b), other components such as an antioxidant, an ultraviolet absorber, a coloring agent, and an inorganic filler can be appropriately compounded.

The composition of the present invention is prepared by adding the components (a) and (b) and, if necessary, other components, followed by dry blending using, for example, a Henschel mixer or a high-speed mixer. 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 above-mentioned slit stretchable film is adhered to a nonwoven fabric, a woven fabric, a plastic film or sheet, or 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.

[0029]

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 produced 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 produced using a metallocene catalyst (Dow Chemical Co., trade name Engage E
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 (trade name NUC3195, manufactured by Nippon Unicar Co., Ltd .; 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, 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) Other components (C): High pressure method low density polyethylene (manufactured by Nippon Unicar Co., Ltd., trade name NUC8506; MI 0.8 g / 10)
Min, density 0.922 g / cm ³ ) Evaluation of film formation stability A film was formed by the inflation method of Example 1 and evaluated according to the following criteria.

○: Bubbles can be formed stably.

×: 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 longitudinal direction (MD) of the film.

Opening property: A relatively outside portion of the raw film wound around a paper tube is cut in a transverse direction (TD) with 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 Peeling 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 of the above samples were superposed 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) 60 parts by weight of the component (a) -1 and 40 parts by weight of the component (b) were dry-blended using a super floater (model SFC-50 manufactured by Kawata Corporation). The mixture was melt-kneaded at 170 ° C. using a twin-screw extruder (Model TEX-30, manufactured by Nippon Steel Works, Ltd.) to obtain pellets composed of the composition of the present invention.

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 test methods described above, and the results are shown in Table 1.

(Examples 2 to 4) Except that the components (a) -1 and / or (b) -1 were replaced with the components shown in Table 1, and the mixing ratios thereof were as shown in Table 1, A composition was obtained in the same manner as in Example 1. Example 1 using the obtained composition
The films having the thicknesses shown in Table 1 were obtained in the same manner as described above, and the physical properties of the films were measured. The results are shown in Table 1.

(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 (c) was used instead of the component (b) -1. 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 1.

[0046]

[Table 1] As is clear from Table 1, the film formed from the composition of the present invention satisfies the elongation strength, strain and rupture strength, and elongation required for 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.

[0047]

EFFECT OF THE INVENTION By using the composition of the present invention, a stretchable film can be stably formed, and
The opening property of the tube at the time of film formation can be improved.
Further, the obtained stretchable film retains physical properties required for members such as gathers of disposable diapers. Furthermore,
Since the composition and film of the present invention are composed of a polyolefin-based polymer, they 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
30-90% by weight of low-density polyethylene containing 8% by weight or more and (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) 10-70% by weight % Of a resin composition for a stretch film. 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.