JP2932541B2 - Extensible film or sheet - Google Patents

Description

The present invention relates to an extensible film or sheet and a method for producing the same. More specifically, the present invention relates to a diaper gather, a diaper back sheet, a film for V-process, a pallet stretch film, and the like, and a film or sheet having excellent extensibility such as flexibility, extensibility, pleasant texture, and feeling, and a method for producing the same. Things.

[Conventional technology and its problems]

Density less than 0.910 g / cm ^3, in particular extruded film consisting of ultra low density ethylene copolymers 0.85~0.90g / cm ³ is less crystalline portions, because the low molecular weight component is large, manufactured by a conventional film forming method When the film is formed, blocking between the films occurs, and since the viscosity is large at a low shearing rate, roughening of the skin is caused.

As a countermeasure, anti-blocking agents such as synthetic silica, lubricants such as metal soaps, or molding methods in which a large amount of a plasticizer or the like is added have been devised, but none of the effects are insufficient.
Conversely, the additive often bleeds, giving rise to a texture, texture and hygiene problem.

Further, when an additive is used, there is a problem that the cost is increased.

Such an ultra-low-density ethylene-based copolymer has excellent extensibility and flexibility as compared with ordinary polyethylene, but it is difficult to produce a practically usable film due to the above-mentioned drawbacks. Was.

[Means for solving the problem]

In view of the above points, the present inventors have conducted intensive studies on a method for producing a film having flexibility and extensibility using an ultra-low-density ethylene-based copolymer. The present inventors have found that a stretchable film having excellent performance can be obtained by modifying a raw material in which a specific linear low-density polyethylene is blended with a polymer with a radical generator to form a film, and have completed the present invention. .

That is, the gist of the present invention density ethylene copolymer 100-60 parts by weight and density of 0.85~0.89g / cm ³ is from 0.910 to 0.94
It is obtained by extruding into a stretchable film or sheet after reacting or reacting 0.001 to 0.1 part by weight of a radical generator to a raw resin consisting of 0 to 40 parts by weight of linear polyethylene of 5 g / cm ^3. An extensible film or sheet having the following physical properties.

1) The blocking property is 60g / 25mm at 180 ° C peel strength measurement value.
2) Tensile strength of 750% or more 3) Elmendorf tear strength of 30 kg / cm or more 4) 1% elastic modulus is in the range of ²⁰ to 2000 kg / cm ² Hereinafter, the present invention will be described in more detail.

The ultra-low-density ethylene copolymer used in the present invention is generally a copolymer of ethylene and an α-olefin having 3 or more carbon atoms (hereinafter, simply referred to as an ethylene copolymer). , The melt index is 10 g / 10 min or less, preferably in the range of 0.1 to 2 g / 10 min, more preferably
In the range of 0.2 to 1 g / 10 minutes, and the density is 0.85 to 0.89 g / cm ³
The flow ratio is 30 or less, preferably 5 to
25, more preferably in the range of 10 to 25. When the melt index is higher than the upper limit, the film becomes too brittle, and when the density is higher than the upper limit, the film lacks softness, the elongation of the film becomes insufficient, and the flow ratio is further increased.
If it is higher than 30, the physical properties of the film deteriorate, which is not preferable. The ethylene copolymer having an elongation of 600% or more, preferably 1000% or more is suitably used.

In the method of the present invention, the melt index is JIS K
It is a value measured at 190 ° C according to 6760, and elongation is JIS K
6301 is a value measured in accordance with the measurement method of elongation at break in the section of tensile test, the density is a value measured in accordance with JIS K 6760, and the flow ratio (FR) Using the above melt index measuring device, a shear force of 10 ⁶ dynes / cm ³
The ratio of (weight 11131G) 10 ⁵ dynes / cm ³ Extrusion of (load 1113 g) (g / 10 min).

As the α-olefin to be copolymerized with ethylene, propylene, butene-1, pentene-1, hexene-1,
4-methylpentene-1 and the like. Among them, propylene and butene-1 are preferred.

The ethylene copolymer in the present invention also includes a terpolymer obtained by copolymerizing ethylene, an α-olefin having 3 or more carbon atoms, and a non-conjugated diene. Examples of such non-conjugated dienes include 1,4-hexadiene, dicyclopentadiene, and ethylidene norbornene.

Ethylene-based copolymers, using Ziegler-Natta catalysts, among others, a catalyst consisting of a vanadium compound such as vanadium oxytrichloride, vanadium tetrachloride and an organoaluminum compound, ethylene and α-olefin, and in some cases non-conjugated diene Can be produced by copolymerizing

The ethylene content of the ethylene copolymer used in the present invention is in the range of 40 to 90 mol%, and the content of α-olefin having 3 or more carbon atoms is in the range of 10 to 60 mol%. Is desirable.

Commercially available ethylene copolymers include NORSOFL marketed by CdF Chimie EP.
EX (FW1600, FW1900, MW1920, SMW2440, LW2220, LW2500, LW2
550), Flex Resin (DFDA1137, DEDA1138, DEFD1210, DEFD9042) marketed by Nippon Unicar, Tuffmer (A4085, A409) marketed by Mitsui Petrochemicals
0, P0180, P0480) JSR marketed by Nippon Synthetic Rubber
-EP (EP02P, EP07P, EP57P) and the like.

The linear polyethylene to be mixed with the ethylene-α-olefin copolymer has a density of 0.910 to 0.945 g / cm ³ ,
Preferably, those having a range of 0.915 to 0.940 g / cm ³ are used. If the density of the linear polyethylene is smaller than the lower limit, problems such as easy blocking and easy surface roughening are caused. If the density is larger than the upper limit, elongation and flexibility are greatly reduced depending on the blending ratio, which is not preferable.

The linear polyethylene has a melt index of 10 g / 10 min or less, preferably 0.2 to 5 g / 10 min, and an elongation of 500% or more, preferably 700% or more. If the melt index is more than 10 g / 10 minutes, film forming is extremely difficult, and if the elongation is less than 500%, the extensibility of the film becomes insufficient, which is not desirable. Further, the flow ratio of the linear polyethylene is 10 to 70,
In particular, the range of 15 to 35 is desirable from the viewpoint of film strength and transparency.

As the linear polyethylene, linear low-density polyethylene (L-LDPE) is generally used. L-LDPE is a copolymer of ethylene and another α-olefin, and is produced by a conventional high-pressure method. Different from branched low density polyethylene resin. The linear low-density polyethylene is obtained by copolymerizing, for example, ethylene with about 4 to 17% by weight, preferably about 5 to 15% by weight of other α-olefins such as butene, hexene, octene, decene, and 4-methylpentene-1. It is manufactured using a Ziegler-type catalyst or a Phillips-type catalyst used in the production of high-density polyethylene with the medium- to low-pressure method. It is suitably reduced to about 0.910 to 0.945 g / cm ³ by utilizing branching, and is a polyethylene having a structure that is more linear than conventional branched low-density polyethylene and more branched than high-density polyethylene.

The blending amount of the ethylene copolymer and the linear polyethylene is 100 to 60 parts by weight of the ethylene copolymer, preferably 100
The linear polyethylene is used in an amount of 0 to 40 parts by weight, preferably 0 to 20 parts by weight with respect to 80 parts by weight. If the blending amount of the linear polyethylene is more than 40 parts by weight, good elongation characteristics and flexibility of the ethylene-α-olefin copolymer are unfavorably reduced.

In the present invention, the raw material resin comprising the above-mentioned ethylene-α-olefin copolymer and linear polyethylene is modified with a radical generator. As the radical generator to be used, the decomposition temperature at which the half-life is 1 minute is 130 ° C. ~ 300 ° C is preferred, for example, dicumyl peroxide, 2,5
-Dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, α, α'-bis (t-butylperoxyisopropyl) ) Benzene, dibenzoyl peroxide,
Di-t-butyl peroxide and the like.

The compounding amount of the radical generator is 0.001 parts by weight based on the total 100 parts by weight of the ethylene copolymer and the linear polyethylene.
To 0.1 part by weight, more preferably selected from the range of 0.01 to 0.1 part by weight, when the compounding amount is more than 0.1 part by weight, the melt index is too low, so that the film tends to be cut during film formation, In addition, the surface of the film is undesirably rough.

In the present invention, a method of blending a radical generator with the ethylene copolymer and the linear polyethylene to decompose the radical generator and react with the polyethylene is not particularly limited, and is carried out, for example, by the following method. can do.

(1) The above-mentioned ethylene copolymer, linear polyethylene, and radical generator are fed simultaneously or sequentially at the time of inflation molding, and are melt-extruded.

(2) The above ethylene-based copolymer, linear polyethylene, and radical generator are kneaded and reacted using a kneader such as an extruder or a Banbury mixer, and then pelletized, followed by inflation molding using the pellets. I do.

(3) A masterbatch containing a large amount of a radical generator, that is, a linear polyethylene or an ethylene-based copolymer is blended with a large amount of a radical generator (usually about 5000 to 10000 ppm). A pelletized masterbatch is prepared in advance by melt-kneading at a temperature at which almost no reaction occurs with polyethylene, and the masterbatch is blended with the above-mentioned ethylene copolymer and linear polyethylene to perform inflation molding.

The radical generator itself is used as it is or dissolved in a solvent.

By reacting the ethylene-based copolymer and the linear polyethylene with a radical generator, the polyethylene causes a molecular coupling to increase a high molecular weight component and obtain a modified polyethylene having a reduced melt index.

Here, the peroxide mainly crosslinks the low molecular weight component, so that the texture of the film surface is improved and the blocking is also prevented.

In the crosslinking reaction with the above radical generator, the melt index at 190 ° C. of the modified polyethylene obtained by the reaction (that is, the modified product of the ethylene copolymer or the blend of the ethylene copolymer and the linear polyethylene). It is desirable that (MI ₂ ) and / or the flow ratio (FR ₂ ) be within the above range. MI ₂ is 5 g / 10 min or less, desirably in the range of 0.05 to 2.0 g / 10 min, and the value of MI ₂ / MI ₁ (melt index of polyethylene before modification) is 0.1 to
0.9, desirably in the range of 0.1 to 0.8 is desirable from the viewpoint of film forming processability and stretchability.

In addition, FR ₂ is in the range of 10 or more, preferably 20 or more, and the value of FR ₂ / FR ₁ (the flow ratio of polyethylene before denaturation) is
It is preferably 1.1 or more, and more preferably 1.1 to 10 from the viewpoint of film forming processing.

In addition, the above-mentioned raw material resin, that is, a modified product of the blend of the above-mentioned ethylene-based copolymer and linear polyethylene, may be used for ordinary polyethylene, if necessary, such as an antioxidant, an ultraviolet absorber, an antistatic agent, and a lubricant. Known additives may be added.

In the present invention, a film or a sheet is formed by extrusion using a modified product of the blend of the ethylene copolymer and the linear polyethylene.

The thickness of the film or sheet can be arbitrarily changed depending on the purpose of use, but is usually in the range of 10 μ to 3000 μ.

As the film or sheet forming method, a normal film or sheet forming method can be applied.In particular, in the blown film forming method, the extrusion temperature is 150 to 250 ° C., and the blow-up ratio is 2 to 2 from an annular die having a lip gap of 0.7 to 4.0 mm.
6. Frost line height 10-100cm, draft rate 3-70
When molding under the conditions described above, a particularly preferred film can be obtained. The draft rate is a value calculated by the following equation.

In the T-die film forming method, the extrusion temperature is 15
Draft rate from die with 0 ~ 250 ℃, lip gap 0.5 ~ 4.0mm
Mold under conditions of 10-40. The draft rate of T-die is
Calculate as BUR = 1.

The physical properties of the film or sheet obtained by extruding the raw material resin are as follows.

(1) The blocking property is 6 when measured at 180 ° peel strength.
0 g / 25 mm or less, preferably 30 g / 25 mm or less. The blocking property is 10 cm from the flat tubular film obtained by inflation molding with the MD direction (take-off direction) as the longitudinal direction.
The sample is cut out into a two-piece strip of × 2.5 cm, the sample is peeled from one end to the center, and the peeled films are fixed to upper and lower chucks of a tensile tester. (The distance between the chucks when fixed was 50 mm.) In this state, the lower chuck was lowered at a speed of 300 mm / min, and the stress at the time when the two films were peeled was determined to be a blocking property value. The measurement temperature is 25 ° C.

If this value is high, the film is plastically deformed when the blocked film is peeled off, which is not preferable.

(2) Tensile elongation of 750% or more, preferably 900% or more If it is less than the lower limit, sufficient extensibility cannot be obtained, which is not preferable.

(3) Elmendorf tear strength of 30 kg / cm or more, preferably 50 kg / cm or more; If it is less than the lower limit, it is not preferable because the film is easily torn (teared) when used for stretchability.

(4) 1% elastic modulus is 20 to 2000 kg / cm ² , preferably 20 to 2000 kg / cm ² .
500Kg / cm ² range If it is less than the lower limit, the film strength is insufficient when used for extensibility, and if it exceeds the upper limit, the film is insufficiently flexible when used for extensibility.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

Example 1 Ethylene-propylene copolymer (melt index (MI): 2.0 g / 10 min, density: 0.89 g / cm ³ , elongation: 1100%, flow ratio: 23, propylene copolymerization amount: 22% by weight) As a radical generator, 2,5-dimethyl-2,5 which is an organic peroxide
0.03% by weight of di (t-butylperoxy) hexyne-3
Mix and mix this with Modern Machinery Co., Ltd., DELSA 40mmφ extruder with annular slit diameter 100mmφ, lip clearance 1.2
Using an inflation molding machine equipped with an inflation die of 0.2 mm and a cooling air ring, the extrusion temperature was 180
C., an extrusion rate of 10 kg / hr, a blow-up ratio (BUR) of 3.0, a frost line height of 32 cm, and a take-up speed of 6.8 m / min.

Table 1 shows the results of measuring various physical properties of the obtained film.

 In addition, the physical property measurement in a table | surface was performed by the following method.

(A) Surface condition of film It was visually determined whether or not so-called shark skin had occurred.

(B) Blocking property of the film From the flat tubular film obtained by the inflation molding, cut out into two strips of 10 cm × 2.5 cm with the MD direction (take-off direction) as a longitudinal direction, from one end to the center of the sample. Is peeled off, and each of the peeled films is fixed to upper and lower chucks of a tensile tester. (The distance between the chucks when fixed was 50 mm.) In this state, the lower chuck was lowered at a speed of 300 mm / min, and the stress at the time when the two films were peeled was determined to be a blocking property value. The measurement temperature is 25 ° C.

(C) Elmendorf tear strength Measured in accordance with JIS P 8116.

The value is shown in the larger one of the TD direction and the MD direction (film taking direction (longitudinal direction)) of the film.

(D) Tensile elongation Measured in accordance with the method for measuring elongation at break in the section of tensile test in JIS K 6301.

The values are shown in either the TD direction or the MD direction of the film in the direction in which the elongation is large.

(E) 1% Elastic Modulus In accordance with JIS K 6301, a tangled piece having a width of 2.5 cm and a length of 1500 mm was pulled at a speed of 10 mm / min, and a stress at 1% elongation was determined.

 The average value in the TD direction and the MD direction of the tangled pieces was shown.

Examples 2 to 3 and Comparative Examples 1 to 4 Molding was performed in the same manner as in Example 1 except that the types and amounts of the blends were as shown in Tables 1 and 2, and the obtained films were evaluated by the following methods. did. The evaluation results are shown in Tables 1 and 2.

[Effects of the Invention] According to the method of the present invention, a film having excellent extensibility and causing no blocking, flexibility, and excellent feeling can be obtained, and a film for a gather portion such as a diaper can be used. It is suitably used as a diaper backsheet film or the like.

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C08L 23:00 (56) References JP-A-59-8740 (JP, A) JP-A-59-152937 (JP, A) JP-A-2 -258232 (JP, A) JP-A-1-156604 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08J 5/00-5/02 C08J 5/12-5/22 B29C 55/00-55/30

Claims (2)

(57) [Claims] To 1. A density ethylene copolymer 100-60 parts by weight and density of 0.85~0.89g / cm ³ consisting of linear polyethylene 0-40 parts by weight of 0.910~0.945g / cm ³ material resin 0.001 ~ 0.1
An extensible film or sheet having the following physical properties, which is obtained by extruding an extensible film or sheet while reacting or reacting parts by weight of a radical generator. 1) The blocking property is 60g / 25mm at 180 ° C peel strength measurement value.
2) Tensile strength of 750% or more 3) Elmendorf tear strength of 30kg / cm or more 4) 1% elastic modulus of 20 to 2000kg / cm ² 2. The stretchable film or sheet according to claim 1, wherein the 1% elastic modulus is 20 to 500 kg / cm ² .