JPH0544107A - Narrow drawn material and packaging cloth - Google Patents

Abstract

PURPOSE:To obtain a narrow drawn material, composed of specific straight- chain polyethylene and ethylene propylene random copolymer and suitable as packaging cloths by use in warp and weft yarns after weaving and knitting. CONSTITUTION:The objective narrow drawn material is composed of (A) 10-90wt.% straight-chain polyethylene having <0.945g/cm<3> density and short- chain branches and (B) 90-10wt.% ethylene propylene random copolymer having 2-12wt.% ethylene content and <=10g/10 min melt flow rate in a narrow drawn material composed of a polyolefin composition. Furthermore, the drawn material is preferably used in warp and/or weft yarns and woven or knitted into packaging cloths.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin stretched product and a packaging cloth. Specifically, a thin stretched product made of a polyolefin composition of a specific linear polyethylene and an ethylene propylene random copolymer, and a low temperature shrinkable material suitable for shrink-wrapping an object to be packaged using the thin stretched product The present invention relates to a packaging cloth.

[0002]

2. Description of the Related Art Conventionally, heat shrinkable films made of polyvinyl chloride, long-chain branched polyethylene or the like have been widely used for shrink wrapping. However, these heat-shrinkable films have the drawback of being inferior in mechanical strength such as tear strength, tensile strength, and abrasion resistance. In addition, because of the notch propagation property, there is a drawback that the packaging film is broken at the corners and projections of the packaged object, which causes various troubles during storage or transportation. For this reason, the conventional heat-shrinkable film is rarely used in the heavy packaging field, and is mainly used in the light packaging field where mechanical damage is relatively small. And in the conventional heat-shrinkable film,
The contents of the packaged item may be limited due to the high temperature at which the shrink pack is formed. Further, the direction and amount of shrinkage are limited by the film forming machine. For example, high shrinkage in the vertical direction, low shrinkage in the horizontal direction, high shrinkage in the vertical and horizontal directions, and vice versa.
Vertical direction low shrinkage Horizontal direction high shrinkage It is impossible to freely select the direction and amount of shrinkage according to the shape and packaging form of the packaged object. In other words, changing the shrinkage behavior of only a part of the total width in the vertical direction and the horizontal direction is a state without any effect. Therefore, it is possible to perform shrink-wrapping of a packaged product having a simple shape, but it is the current situation that desired shrink-wrapping cannot be performed if the packaged product has a complicated shape. In addition, the conventional heat-shrinkable film has a width of 1000 to 1 at the current technical level due to restrictions in film forming technology.
The width of 500 mm is the maximum width that can be manufactured, and for this reason, it has not been used in the heavy packaging field where wide width is required.

[0003]

Therefore, the present inventors have found that
Conventionally, in order to solve the problems of the heat-shrinkable film that has been used for shrink wrapping, intensive research has been repeated, various heat-shrinkable cloths have been proposed, and suitable results have been obtained. For example, in the case of annular packaging of tires, the shrinkage rate is still insufficient and unsatisfactory. However, as a result of further studies, the present inventors have found that a thin stretched product made of a polyolefin composition of a specific linear polyethylene and an ethylene propylene random copolymer exhibits excellent heat shrinkability. .. The present invention has been completed based on such findings.

[0004]

[Means for Solving the Problems] That is, the present invention provides a linear stretched product comprising a polyolefin composition, wherein the polyolefin composition is a linear polyethylene having a short-chain branch having a density of less than 0.945 g / cm ^3. 10 to 90% by weight
And an ethylene-propylene random copolymer having an ethylene content of 2 to 12% by weight and a melt flow rate of 10 g / 10 minutes or less, and 10 to 10% by weight. The present invention also provides
The present invention provides a cloth for packaging, characterized by being woven or knitted using at least a part of a warp yarn and a weft yarn.

The straight-chain polyethylene having a short-chain branch used in the present invention comprises ethylene and propylene; using a catalyst composed of a transition metal compound and an organometallic compound;
Butene-1; 4-methylpentene-1; hexene-1;
It can be obtained by copolymerizing an α-olefin such as octene-1, and the polymerization method thereof is not particularly limited. For example, it can be manufactured by any method such as a gas phase method, a slurry method, a solution method and the like. The density of the obtained linear polyethylene is less than 0.945 g / cm ³ , preferably less than 0.935 g / cm ^{3 and} 0.909 g / cm ³ or more. Density of linear polyethylene is 0.945g / cm ³
When the above is satisfied, the problem of the strength of the cloth does not occur, but the heat shrinkability decreases. As a result, the shrink binding force is lowered, and as a result, the shrink wrapping property is extremely deteriorated. On the contrary,
When the density of the linear polyethylene is less than 0.945 g / cm ³ , problems such as heat shrinkage and other problems are solved.
If it is less than 935 g / cm ^3, it is significantly improved. However, for example, if the density is less than 0.905 g / cm ³ , the stretchability of the film tends to be problematic. The linear polyethylene having a density in the above range needs to have a short branch. The length of the branched chain is not particularly limited, but it is desirable that the number of carbon atoms is 10 or less, and when the branched chain is a long chain as in high-pressure polyethylene, the stretchability is poor and the heat shrinkage tends to be insufficient. It is not preferable because it exists.
Furthermore, the melt flow rate of linear polyethylene (19
0 ℃, 2.16kg, hereinafter referred to as "MFR". ) Is not particularly limited. However, from the viewpoint of strength and heat shrinkability, M
FR is preferably 2.0 g / 10 minutes or less, and MFR is preferably 0.1 g / 10 minutes or more from the viewpoint of moldability and stretchability. Also, the high load melt flow rate (190 ° C., 21.6 kg) / melt flow rate (hereinafter referred to as “HLMFR / MFR”), which is related to stretchability and strength, is preferably less than 40 due to the above-mentioned circumstances.

On the other hand, the ethylene-propylene random copolymer in the present invention can be obtained by a usual method using ethylene and propylene as comonomers, but it is important that the ethylene content is 2 to 12% by weight. That is, when the ethylene content is less than 2% by weight, the heat shrinkability decreases,
As a result, the shrink binding force is reduced, and as a result, the shrink wrapping property is extremely deteriorated. In contrast, the ethylene content is 2
When the content is more than 10% by weight, the heat shrinkability is greatly increased and the shrink wrapping property is improved. However, if the ethylene content exceeds 12% by weight, the drawability is significantly reduced, and the strength is insufficient. In the composition of propylene copolymer and propylene homopolymer, the case where the ethylene content is 2 to 12% by weight is also applicable to the present invention. Further, the MFR of the ethylene-propylene random copolymer used in the present invention needs to be 10 g / 10 minutes or less. That is, when the MFR exceeds 10 g / 10 minutes, the heat shrinkability is significantly reduced, and as a result, the shrink wrapping property is extremely deteriorated. If the MFR is 10 g / 10 minutes or less, there is no particular problem. However, from the viewpoint of film moldability and stretchability, the MFR is preferably 0.5 g / 10 min or more, and from the viewpoint of film moldability, strength and heat shrinkability, MFR is preferably 8 g / 10 min or less.

Further, in the present invention, the composition ratio obtained by mixing the linear polyethylene having a short chain branch and the ethylene-propylene random copolymer is important. That is, 10 to 90% by weight of linear polyethylene having a short chain branch and 90 to 90% of ethylene propylene random copolymer
And 10% by weight. When the composition of the linear polyethylene having a short chain branch exceeds 90 parts by weight and the ethylene-propylene random copolymer is less than 10 parts by weight, the stretchability and strength are insufficient. On the other hand, when the composition of the linear polyethylene having a short chain branch is less than 10 parts by weight and the ethylene-propylene random copolymer is 90 parts by weight or more, the shrinkage rate is lowered. Further, when applied to a packaging cloth, there is a problem that the heat sealability is deteriorated.

There are various methods for producing a thin stretched product composed of a composition containing a straight-chain polyethylene having a short-chain branch having such a blending ratio and an ethylene-propylene random copolymer as main components. For example, first, a film is formed by melt extrusion and cooled. Then, after cooling, a slitter is appropriately slit to have a width, and then heated and stretched to obtain a fine stretched product. This melt extrusion molding can be carried out by a method generally used in the past, for example, an inflation extruder or the like. That is, in melt extrusion molding,
A composition containing a linear polyethylene having a short chain branch and an ethylene-propylene random copolymer as main components is extruded into a film form in a molten state from a slit of a die and cooled. After cooling, after slitting with a slitter, it is possible to obtain a fine stretched product by stretching at a high draw ratio, for example, a draw ratio of 2 to 9 times, preferably in the temperature range of 60 to 120 ° C., to obtain a tape-like product. Can be used as In this stretching process, the heating temperature is 12
If it exceeds 0 ° C, not only the stretchability deteriorates but also slippage occurs between the molecular chains. Therefore, the stretching operation does not contribute effectively to the orientation, and the predetermined strength and heat shrinkage cannot be obtained, which is not preferable. In the above stretching, there is no particular problem if the stretching temperature is less than 120 ° C. However, if the temperature is lower than 60 ° C., whitening may occur, various physical properties may be deteriorated, or the stretchability may be deteriorated. Therefore, it is preferable to perform stretching in the temperature range of 60 to 120 ° C. In particular, the preferred stretching temperature is 70 to 110 ° C., and in this temperature range, the stretchability is excellent, and the physical properties in which the strength, the heat shrinkage rate and the shrinkage temperature are most balanced are obtained. Further, the stretching ratio at the time of stretching depends on the desired strength, but is preferably 4 to 8 times. If the draw ratio is less than 4 times, a problem may occur in the strength of the obtained thin stretched product. Further, if the draw ratio exceeds 8 times, problems may occur in drawability. Then, in order to reduce the natural shrinkability after the stretching process and to prevent the crushing of the paper tube of the winding machine, the heat treatment may be carried out immediately after the stretching process in a state of fixed dimensions. Alternatively, it may be desirable to perform such heat treatment. At the time of melt extrusion molding, a monofilament can be obtained by using a nozzle for a die slit, and a filamentous product having a plurality of monofilaments can be obtained as a thin stretched product.

The filamentous material, monofilament and tape-like material (hereinafter referred to as "filamentous material"), which are the thin stretched products of the present invention having high shrinkability and high strength thus obtained, are part or all of the warp yarn. , Weaving using part or all of the weft or part or all of both the warp and the weft,
By knitting, the shrink wrapping cloth of the present invention can be obtained. The weaving and knitting may be performed by a conventionally used technique of a loom or a knitting machine. The specifications of the filamentous material to be used may be appropriately selected and determined according to the shape of the object to be packaged. For example, when a shrink cloth that shrinks only in the vertical direction (does not shrink in the horizontal direction) is required, use the filamentous material according to the present invention for the warp and use the filamentous material having a low heat shrinkage rate for the weft. Good. On the other hand, when a shrinkable cloth that shrinks only in the horizontal direction and does not shrink in the vertical direction is required, the weaving specification in which the warp and the weft are reversed may be used. Further, when a shrink cloth that shrinks in both the vertical and horizontal directions is required, the filamentous material according to the present invention may be used for both the warp and the weft. Further, for example, in the case of shrink-wrapping an atypical object to be packaged such as an automobile wheel disk, the filamentous material according to the present invention having different heat shrinkage ratios is used as a warp yarn according to the type, and is used as a weft yarn. A filamentous material having a constant heat shrinkage may be used.
The heat shrinkage rate is adjusted by appropriately changing the density of the linear polyethylene having a short chain branch used, the ethylene content of the ethylene-propylene random copolymer, the melt flow rate, the composition ratio, the stretching temperature, the stretching ratio, etc. can do.

As the die slits used in the practice of the present invention, those conventionally used such as T-type dies, circular dies, filament nozzles and band-shaped rectangular nozzles can be used. As the cooling after extrusion molding, any of water cooling, air cooling, contact with a chill roll, and the like can be used.
Further, as the stretching process, any stretching method such as open stretching, roll stretching, wet stretching and hot plate stretching may be used, but since the difference between the melting point and the optimum stretching temperature is large, it is relatively inexpensive and heat control is possible. The use of hot plate stretching, which is easy to perform, is preferred.

If necessary, the polyolefin composition used in the present invention may be mixed with an antioxidant, an ultraviolet ray deterioration preventing agent, a lubricant, a pigment and a different resin. Further, depending on the intended use, the packaging cloth of the present invention may be laminated with a thermoplastic resin according to a conventional method and used. Furthermore, in order to improve mechanical properties such as abrasion resistance, the packaging cloth of the present invention may be laminated by a method such as sandwich lamination in which two or more sheets of the packaging cloth are used and an intermediate layer is sandwiched therebetween. .. When two or more sheets are laminated, the abrasion resistance against vibration is effectively improved because it feels more than the number of sheets.

[0012]

The present invention will be described in more detail below with reference to Production Examples, Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these.

Production Examples 1 to 3 and Comparative Production Examples 1 to 8 Before carrying out the present invention, a film having a thickness of 50 μm was produced by the inflation method for each of the polyolefin compositions shown in Table 1. Then, after slitting with a slitter, it was stretched at a stretching ratio and a stretching temperature shown in Table 1 to obtain a tape of 1000 denier. The results of measuring the tensile strength and the thermal shrinkage are shown in Table 1.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

Example 1 The tape produced in Production Example 1 was used as a warp, and the tape produced in Comparative Production Example 8 was used as a weft to weave a plain weave with a 2700 mm width throughsizer at 10 × 10 yarns / in. Got a cross.

Example 2 One side of the cloth of Example 1 has a density of 0.919 g / cm ³ , MF.
R3g / 10min using low density polyethylene, thickness 25
A low density polyethylene film was laminated to obtain a cloth.

Example 3 A cloth having a density of 0.919 g / c in the middle of two sheets of the cloth of Example 1
A 25 μm-thick layered cloth was obtained using low-density polyethylene having m ³ and MFR of ³ g / 10 min.

Example 4 In Example 2, except that the tape produced in Production Example 2 was used in place of the tape in Production Example 1 as the tape for the warp.
A cloth was obtained in the same manner as in Example 2.

Comparative Example 1 The tape produced in Comparative Production Example 1 was used as a warp, and the tape produced in Comparative Production Example 8 was used as a weft. 10 × 10 / in
The density was 0.919 g / cm ³ , MFR ³ g
A low density polyethylene film having a thickness of 25 μ was laminated using / 10 min of low density polyethylene to obtain a cloth for comparison.

COMPARATIVE EXAMPLE 2 The tape prepared in Comparative Production Example 2 was used as a warp and a weft.
A density of 0.919 g / cm on one side of the cloth obtained by weaving a plain weave with a 2700 mm width throughsizer machine at 0 × 10 fibers / in.
³ , a low density polyethylene film having an MFR of ³ g / 10 min was laminated with a low density polyethylene film having a thickness of 25 μm to obtain a cloth for comparison.

Comparative Examples 3 and 4 Thickness of commercially available linear branched low density polyethylene 15
0 μ shrink film (Comparative Example 3) and polyvinyl chloride 110 μ thick shrink film (Comparative Example 4)
Was purchased for comparison.

Table 2 shows the results of measuring various physical properties of the cloths obtained in Examples and Comparative Examples and commercial products. From Table 2, it can be seen that the cloth according to the present invention is superior in various strengths, heat shrinkability and shrink wrapping property, as compared with Comparative Examples and commercial products.

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

[0028]

[Table 7]

* 1 After soaking in a glycerin bath for 1 minute at each temperature. * 2 Dirt: 38 mm diameter hemisphere, 1 m height. * 3 Car tires (outer diameter 625 mm, inner diameter 355 mm)
With a 5% margin in length, the end is heat-sealed, and the inside of the shrink tunnel takes 20 seconds. The sleeve mouth can shrink to the inner diameter of the tire or less without blocking by the cloth. temperature. * 4 The minimum transit time that can be tightly packed in a shrink tunnel at 185 ° C by heat sealing as in the previous section. * 5 ◎ ・ ・ ・ Very good, ○ ・ ・ ・ Good, × ・ ・ ・ Poor. * 6 The number of times when perforation was observed.

[0030]

Industrial Applicability As in the present invention, a cloth using a polyolefin composition composed of a linear polyethylene having a short chain branch and an ethylene propylene random copolymer as a warp and a weft has various strengths. It also has excellent heat shrinkage, and has heat shrinkable packaging properties. Therefore, when the product of the present invention is applied to heat-shrink packaging, an extremely great effect can be expected.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location D03D 1/00 C 7199-3B 15/02 C 7199-3B (72) Inventor Taiji Ota Nihonbashi Horidome, Chuo-ku, Tokyo 1-315, Machi Heisei Polymer Co., Ltd. (72) Inventor, Ryosuke Kamei, 3-2 Chidoricho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Denko K.K. 3-2 Chidoricho, Ward Showa Denko Kawasaki Resin Research Institute

Claims (2)

[Claims] 1. A thin stretched product comprising a polyolefin composition, wherein the polyolefin composition has a density of 0.945.
Linear polyethylene 1 having a short chain branching of less than g / cm ³
0 to 90% by weight and ethylene content of 2 to 12% by weight,
A thin stretched product, which comprises 90 to 10% by weight of an ethylene-propylene random copolymer having a melt flow rate of 10 g / 10 minutes or less. 2. A packaging cloth comprising the thin stretched product according to claim 1 woven or knitted using at least a part of a warp and a weft.