JP3228706B2 - Shrink packaging material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a shrink wrapping material.

[0002]

2. Description of the Related Art Shrinkable film packaging involves shrinking a film wrapped with sufficient room for heating to make it tightly adhered to the product to form a tight package. It has been used as a packaging to improve the commercial value of conventional products. Conventionally, polyvinyl chloride, polypropylene, low-density polyethylene, ethylene-
Vinyl acetate copolymers and the like are frequently used as raw material resins. However, these heat-shrinkable films have poor mechanical strength such as tear strength and tensile strength, and particularly have insufficient puncture resistance and are not suitable for packaging heavy-weighted objects such as steel. Was.

[0003] In order to solve such a problem, a packaging cloth technology is known which is woven and knitted by using a specific resin as a raw material and using a thread or tape as one or both of a warp and a weft. 62-8534, JP-B-2-53309, JP-A-60-17141 and the like. That is, as a raw material resin, Japanese Patent Publication No. 62-8534 discloses a density of 0.945.
A linear polyethylene having a short-chain branch of less than g / cm ³ is used. Japanese Patent Publication No. 2-53309 discloses that the density is less than 0.935 g / cm ³ and the melt flow rate at high load (190 ° C., 21.6 kg) / 25 to 90 parts by weight of a linear polyethylene having a short chain branch (A) having a melt flow rate (190 ° C., 2.16 kg) of 52 or less and a density of 0.945 g / cm ³ or more Polyethylene (B) 1
A composition comprising 0 to 75 parts by weight is used.
Japanese Patent No. 17141 uses a composition comprising 20 to 90 parts by weight of a linear polyethylene having a short chain branch having a density of less than 0.945 g / cm ³ and 10 to 80 parts by weight of a polypropylene.

[0004]

However, in any of the techniques, a thread or tape made of linear polyethylene having a short chain branch having a density of less than 0.945 g / cm ³ is inferior in stretchability. High strength is not obtained, and when trying to increase the draw ratio to obtain high strength, stretch breakage occurs, and when high-density polyethylene or polypropylene is added to prevent stretch breakage, the heat shrinkage at low temperature decreases. ,
There was a problem that transparency was lost. Accordingly, the present invention provides a shrinkable packaging having a high shrinkage ratio in a low temperature range, a beautiful finish of a shrinkable package, excellent transparency, excellent mechanical strength, particularly excellent puncture resistance, and suitable for packaging of a weight part having a corner. The purpose is to provide materials.

[0005]

Means for Solving the Problems The first invention of the present application is directed to an ethylene / α-olefin copolymer 50 to 50 produced using a metallocene catalyst having the following properties (1) to (4):
90% by weight, and a low-density polyethylene 5 to 50 wt% by high-pressure radical process Furattoya - Ri Na and woven knitted with the warp and / or weft emissions,耐突puncturing strongly
The gist excellent Ru contraction packing material. (1) Melt flow rate is 0.1 to 10 g / 10 mi
n (2) Density is 0.90 to 93 g / cm3 (3) Maximum peak temperature (Tm) by DSC is 80 to 1
25 ° C. (4) Molecular weight distribution (Mw / Mn) is 1.8 to 3.5

The second invention of the present application provides the following (1) to (4)
50 to 90% by weight of an ethylene / α-olefin copolymer produced using a metallocene catalyst having the following properties, and 5 to 50% by weight of a low-density polyethylene obtained by a high-pressure radical method
Consisting of Furattoya - emission Ri Na by laminating a polyethylene resin layer on one or both sides of the textile fabric made by using the warp and / or weft, a gist 耐突thorns strongly superior Ru shrink packaging. (1) Melt flow rate is 0.1 to 10 g / 10 mi
n (2) Density is 0.90 to 93 g / cm3 (3) Maximum peak temperature (Tm) by DSC is 80 to 1
25 ° C. (4) Molecular weight distribution (Mw / Mn) is 1.8 to 3.5

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The ethylene / α-olefin copolymer produced by using the metallocene catalyst used in the present invention is defined as ethylene having the following properties (1) to (4) and ethylene having 3 or more carbon atoms. Ethylene consisting of
It is an α-olefin copolymer.

(1) Melt flow rate (hereinafter referred to as MFR)
Is abbreviated as 0.1 to 10 g / 10 min., Preferably 0.5 to 5 g / 10 min. MFR is 0.1g
/ 10 min., The molding processability is inferior and 10 g / 1.
If it exceeds 0 min., The heat shrinkage of the obtained film is not improved even if the stretching ratio is increased, which is not preferable.

(2) The density is 0.90 to 0.93 g / c
m ³ , preferably 0.90 to 0.93 g / cm ³ . If the density is less than 0.90 g / cm ³ , the stretchability is inferior and the shrinkage binding force is reduced. If the density is more than 0.93 g / cm ³ , the heat shrinkage at low temperatures is undesirably reduced.

(3) The maximum peak temperature (T
m) is from 80 to 125 ° C, preferably from 90 to 120 ° C. If the Tm is less than 80 ° C, the difference from the stretching temperature is too small, and if it exceeds 125 ° C, the optimum stretching temperature is too high, which is not preferable.

(4) The molecular weight distribution (Mw / Mn) is 1.8
To 3.5, preferably 2.2 to 3.0. Mw / Mn
If it is less than 1.8, the moldability is poor, and if it is 3.5 or more, the stretchability is poor, which is not preferable.

The process for producing the ethylene / α-olefin copolymer is described in JP-A-58-19309 and JP-A-5-19309.
JP-A-9-95292, JP-A-60-35005, JP-A-60-35006, JP-A-60-35
No. 007, JP-A-60-35008, JP-A-60-35009 and the like, and can be obtained by copolymerizing ethylene and an α-olefin using a metallocene catalyst.

The metallocene catalyst is, for example, bis (cyclopentadienyl) zirconium dichloride (Cp
₂ ZrCl ₂ ) and a catalyst composed of a metallocene compound typified by methylaluminoxane (MAO) and the like.

The metallocene compound includes a ligand having a cyclopentadienyl ring, a substituted cyclopentadienyl ring substituted with an alkyl group, an indenyl ring, and the like, and hydrogen, a halogen atom, an alkyl group, and the like having zirconium, titanium, or the like. Compounds bonded to transition metals such as hafnium, and specific examples thereof include bis (cyclopentadienyl) zirconium dichloride, bis (methylcyclopentadienyl) zirconium dichloride, and bis (ethylcyclopentadienyl) zirconium dichloride. , Bis (cyclopentadienyl) titanium dichloride, bis (methylcyclopentadienyl) titanium dichloride, bis (ethylcyclopentadienyl) titanium dichloride, bis (cyclopentadienyl) hafnium dichloride, bis (methyl) Cyclopentadienyl) hafnium dichloride, bis (ethyl cyclopentadienyl)
Hafnium dichloride and the like can be mentioned.

An aluminoxane or boron compound can be used as a co-catalyst for the metallocene compound. As the aluminoxane, usually, a chain or cyclic aluminoxane produced by bringing a trialkylaluminum into contact with water is preferable. Representative methylaluminoxane (MAO) can be obtained by reacting trimethylaluminum with water. The metallocene catalyst can be used by being supported on an inorganic oxide or the like.

The polymerization method is not particularly limited, and it is produced by a high pressure method, a solution method, a gas phase method, a slurry method or the like.

As the α-olefin to be copolymerized with ethylene, α-olefins having 3 or more carbon atoms, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-hexene,
Octene, 4-methyl-1-pentene and the like.
Of these, one or more α-olefins may be copolymerized with 5 to 50% by weight, preferably 10 to 30% by weight, of ethylene with 50 to 95% by weight, preferably 70 to 90% by weight. .

On the other hand, the low-density polyethylene produced by the high-pressure radical method used in the present invention means that ethylene is polymerized at a polymerization pressure of
00 to 4000 kg / cm ² , preferably 1000 to 3
Density obtained by polymerization in a tank or tube reactor in the presence of a free radical catalyst and a chain transfer agent under the conditions of 500 kg / cm ² and a reaction temperature of 100 to 400 ° C., preferably 150 to 350 ° C. It is an ethylene polymer of 91 to 0.94 g / cm ³ . The MFR of the low density polyethylene is:
0.1 to 10 g / 10 min. Is preferred, and 0.2 to 2 g.
/ 10 min. Is more preferable.

When the low-density polyethylene is blended with the ethylene / α-olefin copolymer produced using the metallocene catalyst by the high-pressure radical method, the proportion of the ethylene / α-olefin copolymer is as follows. Is 50
The low-density polyethylene is 5 to 50% by weight, preferably the ethylene / α-olefin copolymer is 70 to 90% by weight, and the low-density polyethylene is 10 to 30% by weight. If the low-density polyethylene is more than 50% by weight, the mechanical strength is reduced, especially the puncture resistance is significantly reduced, and if it is less than 5% by weight, the transparency is not sufficient.

In the present invention, the flat yarn is formed by melt-extruding the above-mentioned ethylene / α-olefin copolymer or a mixture of the above-mentioned ethylene / α-olefin copolymer and low-density polyethylene as a raw material using an extruder. A film is formed by a T-die method or an inflation method, and the film once cooled and solidified is slit, then reheated to a temperature at which it can be stretched, stretched, and then heat-treated to form a flat yarn. The stretching temperature is preferably from 70 to 120C, more preferably from 80 to 110C. If the stretching temperature is lower than 70 ° C., whitening occurs and the stretchability decreases, and if it exceeds 120 ° C., the heat shrinkage decreases, which is not preferable. The stretching ratio is preferably 5 to 12 times, more preferably 8 to 10 times. When the stretching ratio is less than 5 times, the heat shrinkage becomes insufficient, and when the stretching ratio is more than 12 times, longitudinal cracks occur, which is not preferable. As a heating method at the time of stretching, any method such as a hot roll method, a hot plate method, an infrared method, and a hot air method can be adopted. The flat yarn has a single yarn fineness of preferably 100 to 2000 denier (hereinafter abbreviated as d), and more preferably 300 to 1000 d.

In the present invention, the above-described flat yarn is woven and knitted using warps and / or wefts to form a shrink wrapping material. As a weaving method, weaving can be performed using a known loom such as a circular loom, a sludge loom, a water jet loom, and various shapes such as plain weave, twill weave and leno weave are applied as the weave structure. You. Further, the knitting method may be either horizontal knitting or vertical knitting, and specific examples include tricot knitting, Milanese knitting, and Russell knitting.

Using the woven and knitted material as a base material,
What laminated | stacked the polyethylene resin layer on this one side or both sides is also used suitably as a shrink packing material. By laminating the polyethylene resin layer, waterproofness and dustproofness are imparted, and a beautifully finished shrinkable package that fits the packaged product can be obtained. As a method for laminating the polyethylene resin layer, a known extrusion lamination method is preferably used. The thickness of the layer provided by the extrusion lamination method,
20 to 100 μm per side is preferred, and 30 to 60 μm
m is more preferred. If it is less than 20 μm, the welding strength in post-processing becomes insufficient, and if it exceeds 100 μm, flexibility is lost, which is not preferable.

Examples of the polyethylene resin include a low-density polyethylene, a linear low-density polyethylene, an ethylene-vinyl acetate copolymer, an ethylene-alkyl acrylate copolymer and a low-density polyethylene obtained by a high-pressure radical method usually used in an extrusion lamination method. Ethylene / α-olefin copolymer produced using a metallocene catalyst alone or
Used as a mixture of more than one species. Among them, the low-temperature extrusion lamination is possible, and the low-temperature shrinkage rate of the formed shrinkable packaging material is improved, so that the ethylene-α-olefin copolymer or the ethylene-α-olefin produced using the metallocene catalyst is used. -A mixture in which 5 to 50% by weight of the low-density polyethylene is blended with respect to the olefin copolymer is preferable.

The polyethylene resin used in the present invention includes an antioxidant, a lubricant, an ultraviolet absorber, a flame retardant, and the like, within a range not departing from the gist of the present invention depending on the purpose of use.
Antistatic agent, pigment, inorganic filler, organic filler, crosslinking agent,
Additives such as a foaming agent and a nucleating agent may be blended.

[0025]

Examples Test method 1. Tensile strength: JISL-1068 2. Tensile elongation: JISL-1068 3. Tear strength: JISL-1079 4. Thermal shrinkage: 100 ° C in ethylene glycol bath
It was immersed for a minute, and the shrinkage ratio before and after immersion was measured. 5. Haze after shrinkage: According to JIS K-7105 6. Puncture resistance: A film is fixed to a wooden frame having an 82 mm aperture, and a jig having a 3/4 inch hemispherical tip at the center thereof is 500 mm / min. The maximum load until the jig was pierced at a speed of. And shown in kgf. 7. Shrink packaging appearance: shrink temperature 1 in shrink tunnel
The product after shrink wrapping is visually observed at 60 ° C. for 20 seconds in a tunnel passing time. Good products without sagging or wrinkles are evaluated as good. ○ Slight sagging or wrinkles are recognized, but there is no problem with productability. Is indicated by ×, and those having a problem with the merchantability are indicated by ×.

EXAMPLE 1 Metallocene-catalyzed ethylene / α-olefin copolymer (MFR = 2.0 g / 10 min., Density = 0.913)
g / cm ³ , Tm = 114 ° C., Mw / Mn = 2.5) 90
% By weight and a low-density polyethylene (MFR = 0.4, density = 0.921 g / 10 min.,
Tm = 112 ° C.) Using a mixture of 10% by weight, a film was formed by inflation, cooled, slitted, stretched at 115 ° C., annealed at 90 ° C., 6.8 times by hot plate contact stretching. By stretching, a flat yarn having a fineness of 1000 d was obtained. Using a flat yarn as a warp yarn, a plain weave fabric was obtained at a driving density of 8.times.8 yarns / inch by a Sulzer loom.

A woven fabric having good stretching stability at the time of forming the flat yarn, good heat shrinkage over a wide temperature range, and excellent mechanical properties and puncture resistance was obtained. When the steel material having the corners was shrink-packed with this woven fabric, a good shrink-wrap product was obtained. Table 1 shows the evaluation results.

Example 2 On both sides of the woven fabric formed in Example 1, an ethylene / α-olefin copolymer (M) was produced using a metallocene catalyst.
FR = 19 g / 10 min., Density = 0.915 g / cm
³ , Tm = 101 ° C., Mw / Mn = 2.8) were melt-extruded at 290 ° C. by extrusion lamination to form a laminate layer having a thickness of 30 μm to obtain a woven fabric laminate.

The woven fabric laminate has a good heat shrinkage over a wide temperature range, excellent mechanical properties, and excellent puncture resistance. A good shrink-wrapped product having good properties was obtained.
Table 1 shows the evaluation results.

Example 3 As a laminate layer on both sides of the woven fabric formed in Example 1,
Metallocene-catalyzed ethylene / α-olefin copolymer (MFR = 2.0 g / 10 min., Density = 0.913)
g / cm ³ , Tm = 114 ° C., Mw / Mn = 2.5) 90
Weight percent and low-density polyethylene (M
FR = 0.4, density = 0.921 g / 10 min., Tm
= 112 ° C), except that a mixture with 10% by weight was used.

The woven fabric laminate has excellent heat shrinkage over a wide temperature range, excellent mechanical properties, and excellent puncture resistance. When the woven fabric is subjected to shrink packing of a steel material having corners, it has excellent transparency. Good shrink-wrapped products having waterproof and dustproof properties were obtained. Table 1 shows the evaluation results.

Comparative Example 1 As a flat yarn raw material, a linear low-density polyethylene (MFR = 0.7 g / 10 min.,
Density = 0.917 g / cm ³ , Tm = 124 ° C., Mw / M
n = 4.5) 90% by weight and low density polyethylene (MFR = 0.4, density = 0.921 g / 1) by high pressure radical method
(0 min., Tm = 112 ° C.) except that a mixture of 10% by weight was used.

[0033] Stretch breaking frequently occurred during flat yarn formation, and stable production was difficult. The obtained woven fabric was weak in all of tensile strength, tear strength and puncture resistance, had poor heat shrinkage in a low temperature range, and had insufficient transparency. Table 1 shows the evaluation results.

Comparative Example 2 An ethylene / α-olefin copolymer (MFR = 2.0 g / 1) using a metallocene catalyst as a flat yarn raw material
0 min., Density = 0.913 g / cm ³ , Tm = 114
90 ° C., Mw / Mn = 2.5) and high-density polyethylene (MFR = 0.7 g / 10 min., Density = 0.95)
7 g / cm ³ ) The same procedure as in Example 1 was carried out except that a mixture of 10% by weight was used.

This woven fabric had an insufficient heat shrinkage in a low temperature range and was excellent in mechanical properties, but was inferior in puncture resistance and transparency and could not obtain a good shrink wrapped product. Table 1 shows the evaluation results.

[0036]

[Table 1]

[0037]

As described above, the present invention relates to a woven knitting method using a flat yarn formed by using a mixture of a specific ethylene / α-olefin copolymer and low density polyethylene for warp and / or weft. Woven and knitted fabric obtained by shrink-wrapping the object to be packaged, has transparency that allows the object to be packaged to be easily visually checked from the top of the packaging material, has excellent low-temperature shrinkage, and has a strong puncture resistance. It is a shrink wrapping material suitable for packaging heavy objects having excellent corners. Further, by laminating a polyethylene resin layer on the woven or knitted fabric, a woven or knitted fabric laminate having waterproof and dustproof properties can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B65D 71/08 B65D 71/08 A D03D 1/04 D03D 1/04 // D01D 5/42 D01D 5/42 D01F 6/30 D01F 6/30 (56) References JP-A-8-290513 (JP, A) JP-A-9-52332 (JP, A) JP-A-8-26356 (JP, A) JP-A-3-56266 (JP, A) A) JP-A-6-255045 (JP, A) JP-A-6-190984 (JP, A) JP-A-8-276542 (JP, A) JP-A-7-238266 (JP, A) JP-A-5 -247421 (JP, A) JP-A-11-200176 (JP, A) JP-A-61-193079 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) D03D 1/00- 27/18 B32B 1/00-35/00 B65D 85/00-85/28

Claims (2)

(57) [Claims] 1. An ethylene / α-olefin copolymer produced by using a metallocene catalyst having the following properties (1) to (4): 50 to 90% by weight; Ri name woven knitted to <br/> using the warp and / or weft emissions,耐突barbs strongly superior Ru shrinkable packaging - Furattoya consisting of 50 wt%. (1) Melt flow rate is 0.1 to 10 g / 10 mi
n (2) Density is 0.90 to 93 g / cm3 (3) Maximum peak temperature (Tm) by DSC is 80 to 1
25 ° C. (4) Molecular weight distribution (Mw / Mn) is 1.8 to 3.5 2. 50 to 90% by weight of an ethylene / α-olefin copolymer produced by using a metallocene catalyst having the following properties (1) to (4): A woven or knitted fabric using 50% by weight of a flat yarn as a warp and / or a weft has a polyethylene resin layer laminated on one or both sides.
Ri,耐突thorn strongly excellent Ru contraction packing material. (1) Melt flow rate is 0.1 to 10 g / 10 mi
n (2) Density is 0.90 to 93 g / cm3 (3) Maximum peak temperature (Tm) by DSC is 80 to 1
25 ° C. (4) Molecular weight distribution (Mw / Mn) is 1.8 to 3.5