JP3227457B2 - 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.

In order to solve such a problem, a thread or tape formed from a linear polyethylene having a short-chain branch having a density of less than 0.945 g / cm ³ as a raw material is prepared by using either a warp or a weft. Or a wrapping cloth technology that is woven and knitted using both (Japanese Patent Publication No. 62-8534).
Gazette).

[0004]

However, the density is 0.9.
Threads or tapes made of linear polyethylene having a short-chain branch of less than 45 g / cm ³ have poor stretchability, so that high strength cannot be obtained. There was a problem that stretching breakage occurred. In addition, the shrinkage ratio in the low temperature range was low, and was insufficient for low temperature shrinkage packaging of food products and the like. Accordingly, the present invention provides a shrinkable packaging having a high shrinkage ratio in a low temperature range, a beautiful finish of the shrinkable package, excellent transparency, excellent mechanical strength, particularly excellent piercing resistance, and suitable for packaging a heavy object having corners. The purpose is to provide materials.

[0005]

The first invention of the present application is directed to a flat yarn comprising an ethylene / α-olefin copolymer produced using a metallocene catalyst having the following properties (1) to (4): the Ri Na and woven knitted with 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

The second invention of the present application provides the following (1) to (4)
A polyethylene-based resin layer is laminated on one or both sides of a woven or knitted fabric using a flat yarn made of an ethylene / α-olefin copolymer produced using a metallocene catalyst having the following properties for warp and / or weft: Do Te Ri,耐突
The gist of the 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

[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 0.1 g /
If it is less than 10 min., The molding processability is inferior and 10 g / 10
If it exceeds 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,
-Octene, 4-methyl-1-pentene and the like. Of these, one or two or more α-olefins are added in an amount of 5 to 50% by weight, preferably 10 to 30% by weight,
It is preferable to copolymerize with 50 to 95% by weight, preferably 70 to 90% by weight of ethylene.

In the present invention, the flat yarn is formed by melt-extruding the ethylene / α-olefin copolymer as a raw material using an extruder, forming a film by a T-die method or an inflation method, and cooling and solidifying the film once. After slitting the formed film, the film is stretched by reheating to a temperature at which stretching is possible, and then heat-treated to form a flat yarn. The stretching temperature is preferably from 70 to 120C, more preferably from 80 to 110C. Stretching temperature is 70 ° C
If the temperature is less than 100 ° C., whitening occurs and the stretchability decreases. 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 preferably has a single yarn fineness of 100 to 20.
00 denier (hereinafter abbreviated as d), more preferably 30
0 to 1000d.

In the present invention, the flat yarn is woven and knitted using the warp and / or the weft to form a shrink wrapping material. As the weaving method, a known loom such as a circular loom, a sulzer loom, a water jet loom, and an air jet loom can be used for weaving. Shape is applied. In addition, weaving knitting method,
Any of vertical knitting may be used, and specific examples include tricot knitting, Miranese knitting, and Russell knitting.

The woven and knitted material is used 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 film layers, a known extrusion lamination method is preferably used. The thickness of the layer provided by the extrusion lamination method is preferably 20 to 100 μm per side, and 30 to 6 μm.
0 μm 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.

The polyethylene resin includes 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 shrink packaging material is improved, so that the ethylene / α-olefin copolymer or the same ethylene / α-olefin produced using the metallocene catalyst is used. -A mixture in which 10 to 40% by weight of the low-density polyethylene is blended with respect to the olefin copolymer is preferable.

In the polyethylene resin used in the present invention, an antioxidant, a lubricant, an ultraviolet absorber, a flame retardant, an antistatic agent, a pigment, an inorganic filler may be used within a range not departing from the spirit of the present invention depending on the purpose of use. And additives such as an organic filler, a crosslinking agent, a foaming agent, and a nucleating agent.

[0023]

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 and calculated. 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. in a tunnel passage time of 20 seconds, and has excellent merchantability without sagging or wrinkling. ○, slight sagging or wrinkling is recognized but no problem in merchantability. Was evaluated as “△”, and “×” having a problem with the productability.

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), form a film by inflation, cool, slit, stretch at 115 ° C., annealing at 90 ° C. hot plate contact stretching. 6.8 times stretching and fineness of 10
00d flat yarn 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 during flat yarn formation, 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 a good heat shrinkage over a wide temperature range, excellent mechanical properties, and excellent puncture resistance. When this 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
The procedure was the same as in Example 1 except that n = 4.5) was used.

[0031] 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.

[0032]

[Table 1]

[0033]

As described above, the present invention relates to a woven or knitted fabric obtained by weaving and knitting a flat yarn formed by using a specific ethylene / α-olefin copolymer for a warp and / or a weft. A woven or knitted fabric laminate obtained by laminating a polyethylene resin, the packaged product is shrink-wrapped, the packaged product has transparency that can be easily visually checked from above the packaging material, and has excellent low-temperature shrinkability, It is a shrink-wrapping material that is excellent in puncture resistance and suitable for packaging heavy objects having corners. The woven / knitted fabric laminate is a shrinkable package having waterproof and dustproof properties.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B65D 71/08 B65D 71/08 C08F 210/16 C08F 210/16 D03D 1/04 D03D 1/04 // D01D 5/42 D01D 5 / 42 D01F 6/30 D01F 6/30 B29K 23:00 B29K 23:00 B29L 9:00 B29L 9:00 (56) References JP-A-8-290513 (JP, A) JP-A-8-26356 (JP JP-A-3-56266 (JP, A) JP-A-6-255045 (JP, A) JP-A-6-190984 (JP, A) JP-A-9-52332 (JP, A) 8-276542 (JP, A) JP-A-7-238266 (JP, A) JP-A-5-247421 (JP, A) JP-A-11-200177 (JP, A) U) (58) Field surveyed (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. Woven knitting using a flat yarn made of an ethylene / α-olefin copolymer produced using a metallocene catalyst having the following properties (1) to (4) as a warp and / or a weft: and Ri name, the 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 2. A woven fabric obtained by using a flat yarn made of an ethylene / α-olefin copolymer produced using a metallocene catalyst having the following properties (1) to (4) as a warp and / or a weft: hen one side or both sides of the cloth Ri name by laminating a polyethylene-based resin layer to,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