JP2621452B2 - Method for producing elastic tape or film - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing an elastic tape or film, and more particularly to a method for producing an elastic tape or film using polyethylene as a main raw material and having good texture and excellent elasticity. About the method.

[Prior Art] Tapes or films having rubber elasticity are used in various fields of daily necessities. As a material, rubber bands and the like have been used for a long time, but in recent years tapes or films made of polyurethane elastomer have been favored due to their flexibility, texture, performance as an elastic body, and the like. It has come to be used.

[Problems to be Solved by the Invention] However, in addition to the problem that polyurethane elastomers are expensive, in particular, when used for disposable products such as disposable diapers, toxic cyanide gas when burned is used. There is a problem that it occurs, and its solution is awaited.

Attempts have been made to produce alternatives using completely harmless polyolefins, especially soft polyolefins. However, although soft polyolefins have a texture similar to that of polyurethane, the performance as an elastic body, especially the recoverability after elongation is insufficient, and those which are still practical can be obtained. Not been.

The present invention solves the above-mentioned conventional problems, and uses a polyolefin as a main raw material, has a texture and an elastic body like polyurethane, and does not generate toxic gas even when incinerated. Moreover, it is an object of the present invention to provide a method for producing an elastic tape or film which is less expensive than polyurethane.

[Means and Actions for Solving the Problems] The method for producing an elastic tape or film of the present invention comprises: a copolymer having ethylene as a main component and having a density of 0.910 g / cm ³ or less; to compositions comprising a linear low density polyethylene 0-40 parts by weight of ~0.945g / cm ^3, extruded into a film or sheet mixture was allowed to or react while reacting a radical generating agent 0.001-0.1 parts by weight Then, the film is stretched in an area ratio of 1.2 to 9 times in the flow direction and / or the direction perpendicular to the flow direction.

That is, the present inventors have solved the above-mentioned problems, and, as a result of earnestly examining a method for producing a harmless and inexpensive elastic tape or film having excellent texture and elasticity, a specific ethylene-α olefin was obtained. By extruding a composition obtained by blending a specific linear low-density polyethylene with a copolymer into a film or a sheet and then stretching under specific conditions, a film or tape excellent in various performances is found to be obtained. The present invention has been completed.

 Hereinafter, the present invention will be described in detail.

In the present invention, a density of 0.91 mainly composed of ethylene
A copolymer of 0 g / cm ³ or less (hereinafter referred to as “ethylene copolymer”) 100 to 60 parts by weight and a linear low density polyethylene having a density of 0.915 to 0.945 g / cm ³ 0 to 40 parts by weight The composition containing is subjected to the reaction, and in this composition, the ethylene copolymer is preferably an ethylene-α-olefin copolymer.
As the ethylene copolymer, preferably, an ethylene-α-olefin copolymer having a density of 0.91 g / cm ³ or less, preferably 0.86 to 0.91 g / cm ³ is used. When the density of the ethylene copolymer is greater than 0.91 g / cm ³ , a tape or film having a favorable texture cannot be obtained.

The ethylene copolymer has a melt index.
10 g / 10 min or less, preferably in the range of 0.1 to 5 g / 10 min, more preferably in the range of 0.2 to 3 g / 10 min, the flow ratio is 30 or less, desirably 5 to 25, and more desirably 10 to 25. Is preferably used. If the melt index is higher than 10 g / 10 minutes, the resulting tape or film becomes brittle,
When the flow ratio is higher than 30, the physical properties of the obtained tape or film deteriorate. As the ethylene copolymer, those having an elongation of 1000% or more, preferably 1200% or more are suitably used.

In the method of the present invention, the melt index is JI
SK6760 is a normative references a value measured in compliance with condition 4 in Table 1 JIS K7210, and the flow ratio, using the melt index instrument, the shear forces 10 ⁶ dynes / cm ² (Load 11131
g) and 10 ⁵ dynes / cm ² (load 1113 g) (g / 10 min)
, And the density is a value measured according to JISK6760.

The method for producing such an ethylene copolymer is not particularly limited, and examples thereof include a method of copolymerizing ethylene and an α-olefin using a Ziegler catalyst. Examples of the α-olefin include propylene, butene, hexene, octene, 4-methylpentene-1 and the like. Further, as a third component, various dienes such as butadiene, 1,4-hexadiene, 1,5-hexadiene, vinylnorbornene, ethylidene norbornene, and dicyclopentadiene may be added and copolymerized. The content of the α-olefin in the ethylene copolymer is usually 10% by weight or more, preferably 15 to 50% by weight. As a commercial product of ethylene copolymer, NORSOFLEX marketed by CdF Chimie EP
(FW1600, FW1900, MW1920, SMW2440, LW2220, LW2500, LW255
0), Flex Resin (DFDA1137, DEDA1138, DEFD1210, DEFD9042) marketed by Nippon Unicar, Tahma (A4085, A4090, P0) marketed by Mitsui Petrochemicals
180, P0480), JSR- marketed by Nippon Synthetic Rubber Co., Ltd.
EP (EP02p, EP07p, EP57p) and the like.

The linear low-density polyethylene blended with the ethylene copolymer has a density of 0.915 to 0.945 g / cm ³ , preferably 0.9
Use those having a range of 15 to 0.940 g / cm ³ . Elastic performance (stretchability) is more effectively imparted to the tape or film obtained by blending the linear low-density polyethylene, but if the density is less than 0.915 g / cm ³ , the linear low-density polyethylene Substantially no compounding effect, and 0.945g
If it is larger than / cm ^{3, the} effect of improving elasticity is reduced, which is not preferable. The linear low-density polyethylene has a melt index of 10 g / 10 minutes or less, preferably 0.1 to 5
Those having a flow ratio of 70 or less, preferably 15 to 40 in g / 10 minutes are suitably used.

In the present invention, the linear low-density polyethylene is obtained by copolymerizing ethylene and another α-olefin, and is different from a branched low-density polyethylene resin produced by a conventional high-pressure method. Such linear low-density polyethylenes include, for example, ethylene and butene, hexene, octene, decene,
It is obtained by copolymerizing methylpentene-1 or the like in an amount of about 4 to 17% by weight, preferably about 5 to 15% by weight, and is produced using a Ziegler type catalyst or a Phillips type catalyst used in the production of a high-density polyethylene at a medium to low pressure. It is a thing. Such reactions, the conventional high-density polyethylene and short branched structure by the copolymerization component, density is obtained by a 0.915~0.945g / cm ³ appropriately reduced by utilizing this short-chain branching, a conventional It is a polyethylene having a structure that is more linear than branched low-density polyethylene and more branched than high-density polyethylene.

In the present invention, the blending amount of the ethylene copolymer and the linear low-density polyethylene is 100 to 60 ethylene copolymers.
The amount is in the range of 0 to 40 parts by weight, preferably 10 to 35 parts by weight of the linear low-density polyethylene based on parts by weight, preferably 90 to 65 parts by weight. If the blending amount of the linear low-density polyethylene is more than 40 parts by weight, the obtained tape or film will not have a favorable texture and the stress required for expansion and contraction will be too high.

As the radical generator to be added to the composition obtained by blending the ethylene copolymer and the linear low-density polyethylene at such a ratio, a half-life of 1 minute, and a decomposition temperature of 120 ° C. to 3 ° C.
Those having a temperature in the range of 00 ° C. are preferred. For example, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butyl) Peroxy) hexyne-3, α, α′-bis (t-butylperoxyisopropyl) benzene, dibenzoyl peroxide, di-t-butyl peroxide and the like.

The amount of the radical generator is 0.001 to 0.1 with respect to the total amount of the ethylene copolymer and the linear low-density polyethylene.
Parts by weight, preferably in the range of 0.005 to 0.05 parts by weight.
If the amount of the radical generator is less than 0.001 part by weight, a sufficient effect of the addition cannot be obtained, and if it is more than 0.1 part by weight, the melt index is too low, and the film tends to be cut during tape or film forming. Also, it may cause skin roughness on the surface of the tape or film, which is not desirable.

In the present invention, a method of blending a radical generator with the composition of the ethylene copolymer and the linear low-density polyethylene to decompose the radical generator and react with the polyethylene is not particularly limited. The method can be carried out simultaneously with or before molding.

The above ethylene copolymer during inflation molding,
The linear low-density polyethylene and the radical generator are fed simultaneously or sequentially and melt-extruded.

The ethylene copolymer, the linear low-density polyethylene, and the radical generator are kneaded using a kneader such as an extruder or a Banbury mixer, and reacted, and then pelletized. Molding is performed by inflation molding using the pellets.

A masterbatch containing a large amount of a radical generator, that is, a linear low-density polyethylene, is blended with a large amount of a radical generator (usually about 5000 to 10,000 ppm), and the radical generator almost reacts with the polyethylene above the melting point of the polyethylene. A masterbatch in the form of pellets is prepared in advance by melt-kneading at a temperature not to be adjusted, and the masterbatch is blended with the ethylene copolymer and the linear low-density polyethylene, followed by inflation molding.

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

The effect of the addition of such a radical generator is obtained by reacting the composition of the ethylene copolymer and the linear low-density polyethylene with the radical generator, whereby molecular coupling occurs in the composition and is obtained. This is considered to be due to exerting a favorable effect on imparting elasticity to the tape or film.

The modified product of the ethylene copolymer and the linear low-density polyethylene thus obtained (hereinafter referred to as “polyethylene resin”) may optionally contain an antioxidant and an ultraviolet absorber. Known additives usually used for polyethylene, such as antistatic agents and lubricants, may be added.

In the present invention, using the polyethylene resin,
An unstretched film or sheet is formed by extrusion, and the unstretched film or sheet is stretched in at least one direction at an area magnification of 1.2 to 9 times to produce a stretched tape or film.

The unstretched film or sheet can be molded by a usual film or sheet molding apparatus and molding method, for example, an inflation molding method using a circular die, a T-die molding method using a T die, and the like.
It can be carried out under molding conditions of up to 200 ° C. and a draft rate of 1 to 50.

The unstretched film or sheet obtained as described above is then stretched. Stretching in the present invention means reducing the film thickness before and after stretching and extending the film in at least one direction so that its surface area becomes 1.2 to 9 times. The stretching is in the longitudinal direction of the film or sheet (the direction in which the film or sheet of the film forming machine is taken off).
(Flow direction) or lateral direction (direction perpendicular to the film or sheet take-off direction) (direction perpendicular to the flow direction)
The stretching is performed by axial stretching or biaxial stretching in the longitudinal and transverse directions.

In the case of uniaxial stretching, the unstretched film or sheet obtained by the T-die method or the inflation method is heated as it is or slit to a predetermined width, for example, by changing the peripheral speed of a stretching roll. This is performed by a method of stretching in the take-off direction, that is, in the longitudinal direction, or a method of heating an unstretched film or sheet having its ends fixed, and stretching the film in the transverse direction by widening the gap.

In the case of biaxial stretching, the unstretched film or sheet obtained by the T-die method or the inflation method is slit or cut to a predetermined width as it is, by successively or simultaneously biaxially stretching. It is. Sequential biaxial stretching is performed either in the longitudinal direction followed by the transverse direction, or vice versa. In the simultaneous biaxial stretching, the time distribution of the stretching in the machine direction and the transverse direction is optional,
For example, the stretching in the longitudinal direction may be continued gradually until the stretching in the transverse direction is completed, or the stretching may be started simultaneously in the longitudinal direction and the transverse direction, or completed in the longitudinal direction first.

When performing biaxial stretching, a tenter method sequential biaxial stretching method and a tubular method simultaneous biaxial stretching method are suitably adopted.

The stretching temperature is desirably in the range of room temperature to 100 ° C., particularly 10 to 80 ° C. Temperature lower than room temperature (for example, 10 ° C
When stretched at the following temperature), the mobility of the molecular chains becomes poor, the draw ratio cannot be increased, and there are many practical problems such as the necessity of a cooling device in operation and condensation of the device, which is preferable. Absent. If the temperature is higher than 100 ° C., the stretching orientation becomes insufficient and sufficient performance cannot be obtained. In addition, the stretched film causes problems such as sticking and winding around a metal roll or the like in a production line.

The stretching speed is in the range of 2 to 40% / sec, preferably 10 to 40% / sec.
It is preferably in the range of 2020% / sec. Stretching speed is 2%
If the speed is lower than / sec, the stretchability is likely to be impaired due to orientational crystallization during the stretching. If the speed is higher than 40% / sec, the deformation of the polymer cannot follow the stretching speed, and the stretch breaks.

The stretching magnification is 1.2 to 9 times, preferably 2 to 5 times, more preferably 3 to 5 times, in at least one direction, in view of the stretching operation method (easiness of stretching) and the physical properties of the obtained stretched film.
The range is up to 5 times. In case of biaxial stretching, area magnification
1.2 to 5 times in the vertical direction of the film within the range of 1.2 to 9 times,
It is preferably in the range of 1.2 to 3 times and 2 times in the lateral direction.
It is preferably in the range of 7 to 7 times, preferably 3 to 5 times. When the stretching area ratio is less than 1.2 times, the effect of improving the strength characteristics and breaking tensile strength of the film is small, which is not preferable. On the other hand, when the ratio is more than 9 times, the stretching operability deteriorates, and a stretched film having satisfactory properties cannot be obtained.

Incidentally, the production of a stretched tape, after slitting the unstretched film or sheet to a predetermined width, and then stretching in the take-off direction by heating, or after stretching the unstretched film or sheet as it is, It may be performed by any method of slitting to a predetermined width.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

Examples 1 to 4 and Comparative Examples 1 to 6 After dry-blending an ethylene-propylene copolymer having the physical properties shown in Table 1 and a linear low-density polyethylene, the temperature was set to 140 ° C. with a single-screw extruder having a cylinder diameter of 50 mmφ. Then, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 was added as an organic peroxide, melt-kneaded and extruded into pellets (the composition of each component is as shown in Table 1). .). This was manufactured by Modern Machinery Co., Ltd., using a DELSA 40mmφ extruder, an inflation molding machine equipped with an inflation die with a circular slit diameter of 100mmφ, a lip clearance of 1.2mm, and a cooling air ring.
r, blow-up ratio (BUR) 3.0, frost line height 32c
m, and a take-up speed of 6.8 m / min. were blown-molded to obtain a 30 μm-thick inflation film.

The obtained blown film was longitudinally stretched at a stretching temperature shown in Table 1 to a magnification shown in Table 1 by a longitudinal uniaxial stretching machine. After that, when the transverse stretching was carried out, this was carried out (however, no stretching was carried out in Comparative Example 3). The stretching temperature indicates the temperature at the stretching point.

The obtained film was evaluated by examining the recoverability after elongation by the following method.

A strip cut in the MD (vertical) direction or TD (horizontal) direction with a width of 2.5 cm and a length of 10 cm is pulled up to 200% at a chuck head of 5 cm and a crosshead speed of 300 mm. The head was reversed, and the recovery after elongation was evaluated based on the return elongation at which the crosshead stress became zero.

 When the return elongation exceeded 150%, the recoverability was determined to be good.

The stretched film was not heat-fixed at a high temperature, but was evaluated after being returned to a natural length in about 30 seconds.

The results are shown in Table 1. It is clear from Table 1 that the method of the present invention provides a film having good stretchability.

[Effects of the Invention] As described in detail above, according to the method for producing an elastic tape or film of the present invention, a tape or film having a good texture and a remarkably excellent elasticity such as recoverability after elongation. Are provided easily, efficiently and inexpensively. Moreover, since the tape or film produced according to the present invention is harmless containing polyethylene as a main component, there is no problem of generating harmful gases when incinerated.
It can be used safely in a wide range of fields.

Claims (1)

(57) [Claims] (1) 100 to 60 parts by weight of a copolymer containing ethylene as a main component and having a density of 0.910 g / cm ³ or less, and a density of 0.915 to 0.945 g / cm ³
The composition containing 0 to 40 parts by weight of a linear low-density polyethylene is extruded into a film or sheet after reacting or reacting 0.001 to 0.1 part by weight of a radical generator, and then in the flow direction. And / or stretching in a direction orthogonal to the flow direction at an area magnification of 1.2 to 9 times.