JPH02258232A - Manufacture of elastic tape or film - Google Patents

Abstract

PURPOSE:To manufacture an elastic tape or film which is superior in the hand and elasticity, harmless and inexpensive, by a method wherein a composition obtained by compounding specific, linear and low density polyethylene with a specific ethylene-alpha-olefin copolymer is extrusion-molded and orientation-treated under a specific condition. CONSTITUTION:A composition containing a 100-60 pts.wt. copolymer consisting mainly of ethylene and having density of not exceeding 0.910g/cm<3> and 0-40 pts.wt. linear and low density polyethylene whose density is 0.915/0.945g/cm<3> is extrusion-molded into a filmy or sheetlike state while reacting or after raction of a 0.001-0.1 pts.wt. radical generator on the composition. Then the same is stretched 1.2-9 times in the area magnification in its flowing direction and/or in a direction meeting at right angles with the flowing direction. It is preferably that the stretching temperature is at least at a room temperature and not higher than 100 deg.C, especially that falling within a range of 10-80 deg.C. When stretching is performed at a temperature lower than the room temperature, mobility of a molecular chain becomes little and a draw ratio is not improved. In the case where the same exceeds 100 deg.C, stretching becomes insufficient and sufficient property is not obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing an elastic tape or film, and in particular, the production of an elastic tape or film that uses polyethylene as a main raw material and has a good texture and excellent elasticity. Regarding the method.

[Prior Art] Rubber elastic tapes or films are used in various fields of daily necessities. Materials such as rubber bands have been used in the past, but in recent years tapes or films made from polyurethane elastomers have become popular due to their flexibility, texture, and performance as elastic bodies. It has started to be used.

[Problems to be solved by the invention] However, polyurethane elastomers have the problem of high cost and, especially when used in disposable products such as disposable diapers, emit toxic cyanide gas when incinerated. There is a problem in that this occurs, and a solution to this problem is awaited.

Therefore, attempts have been made to produce an alternative to this using completely harmless polyolefins, especially soft polyolefins. However, although products made of soft polyolefin have a feel comparable to those made of polyurethane, their performance as elastic bodies, especially their recovery after elongation, is insufficient, and they are still not suitable for practical use. has not been obtained.

The present invention solves the above-mentioned conventional problems and uses polyolefin as the main raw material, has a texture similar to polyurethane and the performance as an elastic body, and does not generate toxic gas when incinerated. It is an object of the present invention to provide a method for manufacturing an elastic tape or film that is cheaper than polyurethane.

[Means and effects for solving the problem] The method for manufacturing the elastic tape or film of the present invention is based on the elastic tape or film having a density of 0.910 g/cn? The following copolymer 100 to 60 weight and density 0.915 to 0.945
g/cn? A composition containing 0 to 40 parts by weight of linear low-density polyethylene is extruded into a film or sheet while or after reacting with o, oot to 0.1 parts by weight of a radical generator, Then, in the flow direction and/or in the direction perpendicular to the flow direction, the area magnification is 1.2 to 9.
It is characterized by being stretched twice.

That is, as a result of extensive research into a method for solving the above-mentioned problems and manufacturing a harmless and inexpensive elastic tape or film with excellent texture and elasticity, the present inventors have developed a method for producing a specific ethylene-α olefin. We have discovered that by extruding a composition containing a copolymer and a specific linear low-density polyethylene into a film or sheet, and then stretching it under specific conditions, a film or tape with excellent various properties can be obtained. , completed the present invention.

The present invention will be explained in detail below.

In the present invention, the density of ethylene is 0.9 as the main component.
100 to 60 parts by weight of a copolymer of 10 g/arrI or less (hereinafter referred to as "ethylene copolymer"), and a density of 0.9
15~0.945 g/err? A composition containing 0 to 40 parts by weight of linear low density polyethylene is subjected to the reaction,
In this composition, the ethylene copolymer is preferably an ethylene-α olefin copolymer. Hereinafter, preferably those in the range of 0.86 to 0.91 g/c are used. The density of the ethylene copolymer is 0.91 g/crt
If it is larger, a tape or film with a preferable texture cannot be obtained.

Further, the ethylene copolymer has a melt index of 1
0 g/l 0 minutes or less, preferably 0.1-5 g/l
0 minutes, more preferably 0.2 to 3 g/10 minutes, and a fluidity ratio of 30 or less, preferably 5 to 25, more preferably 10 to 25. If the melt index is higher than 10 g/l 0 min, the tape or film obtained will become brittle, and if the flow ratio is higher than 30, the physical properties of the tape or film obtained will deteriorate. As the ethylene copolymer, one having an elongation of 1000% or more, preferably 1200% or more is suitably used.

In addition, in the method of the present invention, the melt index is J!
Table 1 of JISK7210, which is a reference standard for 5K6760
The flow ratio is the value measured in accordance with Condition 4 of (g/10 minutes), and the density is a value measured in accordance with JIS K6760.

Although there are no particular limitations on the method for producing such an ethylene copolymer, examples include a method of copolymerizing ethylene and α-olefin using a Ziegler catalyst. Examples of α-olefins include propylene, butene, hexene, octene, 4-methylpentene-1, and the like. Furthermore, the third
Ingredients: butadiene, 1.4-hexadiene, 1.5
- The α-olefin content in the ethylene copolymer, which may be copolymerized by adding various dienes such as hexadiene, vinylnorbornene, ethylidenenorbornene, and dicyclopentadiene, is usually 10% by weight or more, preferably 1
As a commercially available ethylene copolymer in the range of 5 to 50% by weight, N0R3OFLEX (FWI 6
00°FW1900. MW1920. SMW2440°LW2220. LW2500. LW2550), flex resin (DFD) coated by Nippon Unicar Co., Ltd.
A113), DEDAI 138. DEFD1210.
DEFD9042), Tafuma (A4085゜A409Q, PO180, PO
480), JSR- manufactured by Japan Synthetic Rubber Co., Ltd.
EP (EP02p, EPO7p, EP57p), etc. are mentioned.

The linear low density polyethylene to be blended with the above ethylene copolymer has a density of 0.915 to 0.945 g/cm",
Preferably, one in the range of 0.915 to 0.940 g/C- is used. Elastic performance (stretchability) of tape or film obtained by blending linear low-density polyethylene
is applied more effectively, but its density is 0.915g
/cm' If it is less than 0.945g/cm', the blending effect of linear low density polyethylene will not be substantially expressed, and if it is less than 0.945g/cm'
crr? If it is larger than this, it is not preferable because the effect of improving elasticity decreases.Also, for linear low density polyethylene, the melt index is 10 g/10 minutes or less, preferably 0.1 to 5 g/10 minutes, and the flow ratio is 70 or less, preferably in the range of 15 to 40, is suitably used.

In addition, in the present invention, linear low density polyethylene is
It is obtained by copolymerizing ethylene and other α-olefins, and is different from branched low-density polyethylene resins produced by conventional high-pressure methods. Such linear low-density polyethylene contains, for example, ethylene and other α-olefins such as butene, hexene, octene, decene, 4-methylpentene-1, etc. in an amount of about 4 to 17% by weight, preferably 5% by weight.
It is a copolymerized product of about 15% by weight, and is produced using a Ziegler type catalyst or a Phillips type catalyst used in the production of medium-low method high-density polyethylene. Through such a reaction, conventional high-density polyethylene is made into a short branched structure by copolymerization components, and the density is appropriately lowered to 0.915 to 0.94 by utilizing this short chain branching.
5 g/crd, and is polyethylene with a structure that is more linear than conventional branched low-density polyethylene and more branched than high-density polyethylene.

In the present invention, the blending amount of the ethylene copolymer and linear low density polyethylene is 100 to 6
0 parts by weight, preferably 90 to 65 parts by weight, to 0 to 40 parts by weight, preferably 10 to 3 parts by weight of linear low density polyethylene.
The range is 5 parts by weight. If the amount of linear low-density polyethylene is more than 40 parts by weight, the resulting tape or film will not have a favorable feel, and the stress required for expansion and contraction will become too high, which is not preferred.

The radical generator to be added to the composition formed by blending the ethylene copolymer and linear low density polyethylene in such proportions has a half-life of 1 minute and a decomposition temperature of 120°C to 120°C.
A temperature range of 300°C is preferable, such as dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-
Di(t-butylperoxy)hexyne-3, α.

Examples include α-bis(t-butylperoxyisopropyl)benzene, dibenzoyl peroxide, di-1-butyl peroxide, and the like.

The blending amount of the radical generator is o, oot~ with respect to the total amount of the above ethylene copolymer and linear low density polyethylene.
The range is 0.1 part by weight, preferably o, oos to 0.05 part by weight. If the amount of the radical generator is less than o, oot parts by weight, sufficient effects cannot be obtained by its addition;
If the amount is more than 0.1 part by weight, the melt index becomes too low and film breakage is likely to occur during tape or film molding, and the surface of the tape or film becomes rough, which is undesirable.

In the present invention, the method of blending a radical generator into the composition of the ethylene copolymer and linear low density polyethylene, decomposing the radical generator and reacting with the polyethylene is not particularly limited, but for example, Method (2) can be carried out simultaneously with molding or before molding.

■ During inflation molding, the above ethylene copolymer,
Linear low density polyethylene and a radical generator are fed simultaneously or sequentially and melt extruded.

(2) Using a kneading machine such as an extruder or a Banbury mixer, the above-mentioned ethylene copolymer, linear low-density polyethylene, and radical generator are kneaded and reacted, and then pelletized. The molding is performed by inflation molding using the pellet.

■ A masterbatch containing a large amount of a radical generator, that is, a large amount of a radical generator (
A masterbatch is prepared in advance by melting and kneading it into a pellet shape at a temperature above the melting point of polyethylene at which the radical generator hardly reacts with polyethylene, and this masterbatch and the above ethylene The copolymer and linear low density polyethylene are blended and inflation molded.

Note that the radical generator itself may be used as it is or dissolved in a solvent.

The effect of adding such a radical generator is that by reacting the composition of the ethylene copolymer and linear low density polyethylene with the radical generator, molecular coupling occurs within the composition. This is thought to be due to the favorable effect on imparting elasticity to the resulting tape or film.

Note that the modified composition of the ethylene copolymer and linear low-density polyethylene obtained in this way (hereinafter referred to as "polyethylene resin") may contain antioxidants and ultraviolet absorbers as necessary. , antistatic agents, lubricants, and other known additives commonly used in polyethylene may be added.

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

For forming the unstretched film or sheet, a conventional film or sheet forming apparatus and forming method, such as an inflation molding method using a circular die, a T-die molding method using a T die, etc., can be used, and the polyethylene resin temperature is 130
~200t: The molding can be carried out under a draft rate of 1 to 50.

The unstretched film or sheet obtained as described above is then subjected to a stretching treatment. Stretching in the present invention refers to reducing the film thickness and increasing the surface area by 1.2 to 9 times before and after stretching. This means that it rotates in at least one direction. The stretching is in the longitudinal direction of the film or sheet (the direction in which the film or sheet is taken up by the film forming machine)
(the machine direction) or the transverse direction (the direction perpendicular to the direction in which the film or sheet is taken) (the direction perpendicular to the machine direction), or biaxially in the longitudinal and transverse directions. It is done.

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, and for example, by changing the peripheral speed of the stretching roll. , a method of stretching in the take-off direction, that is, a longitudinal direction, or a method of heating an unstretched film or sheet with its edges fixed and stretching the film or sheet in the transverse direction by widening the interval.

In the case of biaxial stretching, the unstretched film or sheet obtained by the T-die method or the inflation method is subjected to sequential biaxial stretching or simultaneous biaxial stretching of the unstretched film or sheet obtained by the T-die method or the inflation method, either as it is or after slitting it to a predetermined width. It will be done. Sequential biaxial stretching is carried out either by longitudinal stretching followed by transverse stretching or vice versa. In addition, in simultaneous biaxial stretching, the time distribution of stretching in the longitudinal direction and the transverse direction can be arbitrarily determined. For example, stretching may be continued gradually in the longitudinal direction until the stretching in the transverse direction is completed, or This is done by completing the horizontal direction at the same time, or by completing the vertical direction first.

When performing biaxial stretching, a tenter sequential biaxial stretching method and a tubular interstitial biaxial stretching method are suitably employed.

It is desirable that the stretching temperature is in the range of room temperature or higher and 100°C or lower, particularly 10 to 80°C. If the stretching is performed at a temperature lower than room temperature (e.g., 10°C or lower), the mobility of the molecular chains will be poor and the stretching ratio will be reduced. In addition to not being able to raise the temperature, there are many practical problems such as requiring a cooling device and condensation on the equipment, which is undesirable.If the temperature exceeds 100℃, the stretching orientation will be insufficient and the performance will not be sufficient. In addition to not being able to obtain a stretched film, it is also undesirable because it causes problems such as the stretched film sticking to and wrapping around metal rolls in the production line.

Further, the stretching speed is in the range of 2 to 40%/sec, preferably 1
It is preferable that the stretching speed is in the range of 0 to 20%/sec. If the stretching rate is slower than 2%/sec, the stretchability is likely to be inhibited by oriented crystallization during stretching, and if it is faster than 40%/sec, the polymer may be deformed. It becomes impossible to keep up with the stretching speed, causing stretching breakage.

The stretching ratio in at least one direction is 1.2 to 9 times, preferably 2 to 5 times, more preferably 3 times, in terms of the stretching operation method (easiness of stretching) and the physical properties of the obtained stretched film.
~5 times the range.

In the case of biaxial stretching, the area magnification is within the range of 1.2 to 9 times, and the longitudinal direction of the film is 1.2 to 5 times, preferably 1.
If the above-mentioned stretching area magnification is less than 1.2 times, the film strength This is not preferable because the effect of improving the properties and tensile strength at break is small, and if it is greater than 9 times, the stretching operability deteriorates and a stretched film with satisfactory properties cannot be obtained.

Note that the stretched tape is produced by slitting the unstretched film or sheet to a predetermined width, then heating and stretching it in the take-up direction, or by heating and stretching the unstretched film or sheet as it is, and then This may be done by any method including slitting to a predetermined width.

C Example The present invention will be explained in more detail by referring to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Examples 1 to 4, Comparative Examples 1 to 6 After tri-blending an ethylene-propylene copolymer with physical properties shown in Table 1 and linear low-density polyethylene, the mixture was heated to 140°C using a single-screw extruder with a cylinder diameter of 50 mmφ. 2,5-dimethyl-2,5-di(t-
Butylperoxy)hexyne-3 was added, melt-kneaded and extruded into pellets (the composition of each component is shown in Table 1).
φ extruder has an annular slit diameter of 1o.

mm-, using an inflation molding machine equipped with an inflation die with a lip clearance of 1.2 mm and a cooling air ring, an extrusion temperature of 150°C, and an extrusion amount of 10 kg/
hr, blow-up ratio (BUR)3. Inflation molding was carried out under the conditions of a frost line height of 32 cm and a take-up speed of 6.8 m/min to obtain a blown film with a thickness of 30 μm.

The obtained blown film was longitudinally stretched to the stretching ratio shown in Table 1 using a longitudinal uniaxial stretching machine at the stretching temperature shown in Table 1. After that, for those that undergo lateral stretching,
This was carried out (However, in Comparative Example 3, no stretching was performed.) Note that the stretching temperature indicates the temperature at the stretching point.

The resulting film was evaluated by examining its recovery properties after stretching using the method described below.

Width 2.5cm, length 10cm in MD (vertical) direction or TD
The strips cut out in the (horizontal) direction are chucked with a distance of 5 cm
The crosshead was stretched to 200% at a crosshead speed of 300 mm, and immediately after being stretched to 200%, the crosshead was reversed, and the recovery property after stretching was evaluated based on the return elongation at which the crosshead stress became 0.

When the return elongation exceeded 150%, the recovery property was considered to be good.

Note that the stretched film was not heat-set at a particularly high temperature, but was allowed to return to its natural length within about 30 seconds before evaluation.

The results are shown in Table 1. From Table 1, it is clear that according to the method of the present invention, a film with good stretchability can be obtained.

[Effects of the Invention] As detailed above, according to the method for producing an elastic tape or film of the present invention, a tape or film with a good texture and extremely excellent performance as an elastic body such as recovery after elongation can be obtained. can be provided easily, efficiently, and inexpensively.

Moreover, since the tape or film produced according to the present invention is harmless and mainly consists of polyethylene,
There is no problem of generating harmful gases when incinerated, and it can be used safely in a wide range of fields.

Agent: Patent attorney Tsuyoshi Shigeno

Claims (1)

[Claims] (1) Density 0.910g/cm mainly composed of ethylene
^3 or less copolymer 100 to 60 parts by weight and density 0.9
0.001 to 40 parts by weight of linear low density polyethylene of 15 to 0.945 g/cm^3
While reacting or after reacting 0.1 parts by weight of a radical generator, extrusion molding is performed into a film or sheet, and then the area magnification is 1.2 to 9 times in the flow direction and/or the direction orthogonal to the flow direction. A method for producing an elastic tape or film, the method comprising stretching the elastic tape or film.