JP3483651B2 - Polyolefin-based laminated film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent surface printability,
The present invention also relates to a polyolefin-based laminated film having excellent fusing seal strength at a gusset portion. [0002] Hitherto, it has been known that polyolefin polymer films have poor printability due to non-polarity.
In order to improve this, a corona discharge treatment is performed on the film surface. However, when the corona discharge-treated polyolefin-based polymer film is used for a gusset-filled packaging bag with the corona discharge-treated surface as the outer surface of the bag, the fusing seal strength of the gusset portion is reduced and cannot be used for practical use. There was a problem. For this reason, when using a polyolefin-based polymer film for gusseted packaging bags, a special printing ink is used instead of performing corona discharge treatment on the film surface to prevent a decrease in the fusing seal strength at the gusset. It had been. However, even if a special printing ink is used, the adhesion between the film and the printing ink is insufficient, and the problem of ink dropout due to oil or friction between the film surfaces during transportation remains. Under the circumstances. SUMMARY OF THE INVENTION An object of the present invention is to provide a polyolefin-based laminated film which imparts printability to the film and at the same time reduces the strength of the fusing seal at the gusset portion. SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above-mentioned object, and is intended to provide a polyolefin laminate using a specific resin composition for a surface layer to be subjected to corona discharge treatment. The present invention has been completed on the basis of new findings confirmed by the present inventors that the film has excellent printability and that the strength of the fusing seal at the gusset portion is small.
That is, according to the present invention, the molecular weight distribution (Mw / Mw) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn).
n) a layer of a resin composition comprising 50 to 99% by weight of a crystalline propylene polymer of 2.5 to 4.0 and 50 to 1% by weight of a low crystalline or amorphous olefin polymer; On one surface layer , the surface layer
It is subjected to electric treatment and has a wet tension of 33 to 38 dynes and
Zet fusing seal strength is more than 1180g / 15mm
A polyolefin-based laminated film is provided. [0005] The crystalline propylene polymer used in the present invention has a molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 2.5 to 4.0. Is important. When the molecular weight distribution of the crystalline propylene-based polymer exceeds 4.0,
The effect of improving the fusing seal strength, which is the original object of the present invention, is not recognized. On the other hand, those having a strength of less than 2.5 are not preferable because production becomes extremely difficult. The degree of crystallinity of the crystalline propylene polymer used in the present invention may be any as long as the degree of crystallinity by X-ray diffraction measurement exceeds 30%. As the crystalline propylene polymer in the present invention, known polymers can be used without any limitation as long as they have the above-mentioned crystallinity and molecular weight distribution.
Specific examples of the crystalline propylene polymer in the present invention include, for example, a homopolymer of propylene, a binary copolymer of propylene and ethylene, propylene, and an α-olefin having 4 to 10 carbon atoms. Binary copolymers, propylene-ethylene-α-olefin terpolymers and the like can be mentioned. In the present invention, these polymers or copolymers can be used alone or in combination of two or more. In particular, if the ethylene component is 1 to 1
A crystalline propylene-ethylene copolymer containing 0 mol% can be suitably used. The crystalline propylene polymer used in the present invention has a melt flow index (230 ° C., 2.1
6 kg load, 10 minutes, hereinafter abbreviated as MI. )
1 to 50 in terms of extrusion characteristics or film forming property
g / 10 minutes, preferably 5 to 40 minutes.
More preferably, the range is g / 10 minutes. The crystalline propylene-based polymer in the present invention has a special molecular weight distribution as described above, and it is difficult to obtain a polymer having such a molecular weight distribution by a general polymerization operation. For this reason, it can be suitably manufactured by mixing a radical generator with a crystalline propylene polymer that has been polymerized in advance, and heating the mixture in a solvent or an extruder. From the viewpoint of productivity, a method of kneading and heating in an extruder is preferably used. As the radical generator, known compounds can be used without any limitation. Typical examples thereof include ketone peroxides such as methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide and cyclohexanone peroxide; Diacyl peroxides such as ruperoxide, lauroyl peroxide and benzoyl peroxide; hydroperoxides such as diisopropylbenzene hydroperoxide; dicumyl peroxide; 2,5-dimethyl-2,5-di-
(T-butylperoxy) hexane, 1,3-bis-
(T-butylperoxy-isopropyl) -benzene,
Di-t-butyl peroxide, 2,5-dimethyl-
2,5-di- (t-butylperoxy) -hexane-3
Peroxyketals such as 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane and 2,2-di- (t-butylperoxy) -butane; t- Organic peroxides such as alkyl peresters such as butylperoxy-pivalate and t-butylperoxybenzoate; and percarbonates such as t-butylperoxyisopropyl carbonate. The amount of the radical generator used is not particularly limited, but can be determined in consideration of the decomposition ability of the radical generator, the MI of the obtained crystalline propylene polymer, the molecular weight distribution, and the like. The low-crystalline or non-crystalline olefin polymer used in the present invention is a known olefin polymer as long as it is an α-olefin polymer having a crystallinity of 0 to 30% by X-ray diffraction measurement. A system polymer can be used. Examples of such an olefin-based polymer include an ethylene-butene-1 copolymer, a propylene-butene-1 copolymer, and an ethylene-propylene-butene-1 copolymer. Commercially available products include, for example, “Tuffmer A4085” and “Tuffmer P0” manufactured by Mitsui Petrochemical Co., Ltd.
280 "(both are trade names). MI (230) of a low crystalline or amorphous olefin polymer
° C, 2.16 kg load, 10 minutes) is 0.5 to 40
g / 10 minutes, preferably 1 to 20
More preferably, the range is g / 10 minutes. The mixing ratio of the crystalline propylene polymer and the low-crystalline or amorphous olefin polymer used in the present invention is such that the former is 50 to 99% by weight when the total amount of both is 100% by weight. %, The latter must be 50 to 1% by weight. 5 crystalline propylene polymers
When the amount is less than 0% by weight, the original effect of improving the fusing seal strength is insufficient. On the other hand, when the amount exceeds 99% by weight, the surface of the film may be roughened or a lubricant added to the resin may be used.
Bleeding to the surface of an antistatic agent, an antifogging agent, etc. is slow, which is not practical. Considering the effect of improving the fusing seal strength and the surface roughness of the film, the former is preferably in the range of 70 to 97% by weight, and the latter in the range of 30 to 3% by weight. A resin composition obtained by mixing the above-mentioned crystalline propylene polymer and a low-crystalline or amorphous olefin polymer forms at least one surface layer of the polyolefin laminate film of the present invention. The surface layer composed of the resin composition may be single-sided or double-sided. As the substrate layer on which the surface layer is to be laminated, it is preferable to use a crystalline polyolefin from the viewpoint of being compatible with the above-mentioned resin composition as the surface layer. As the crystalline polyolefin, similar to the above-mentioned crystalline propylene-based polymer, known polyolefins such as propylene homopolymer and propylene-ethylene copolymer can be used as long as the degree of crystallinity by X-ray diffraction measurement exceeds 30%. Polymers, propylene-based polymers such as propylene-ethylene-butene-1 copolymer; high-density polyethylene, low-density polyethylene,
Ethylene polymers such as ethylene homopolymers such as medium density polyethylene, and ethylene-α-olefin copolymers such as linear low density polyethylene can be used. Of course, a crystalline propylene-based polymer which is one component of the resin composition for forming the surface layer described above can also be used. These polymers can be used alone or as a mixture of two or more different types. [0013] Among the various resins described above, a propylene polymer or a linear low-density polyethylene can be suitably used. In the case of a propylene-based polymer, the content of an α-olefin copolymerized with propylene is, for example, in the range of 0 to 10 mol% for ethylene and 0 to 10 mol% for butene-1. (230 ° C, 2.16k
g load for 10 minutes) is preferably 0.5 to 30 g / 10 minutes, and more preferably 5 to 20 g / 10 minutes. The linear low-density polyethylene described above includes ethylene as a main component and α-olefin having 4 to 10 carbon atoms in 0.1 to 1 carbon.
0 mol%, and the density is 0.880 to 0.940 g /
cm ³ , MI (190 ° C., 2.16 kg load, 1
(0 min) of 0.5 to 10 g / 10 min can be suitably used. In the present invention, when only one surface of the base material layer is laminated with the resin composition, the other surface may not be laminated at all, Of polyolefins. As the other polyolefin, the crystalline polyolefin described for the base layer can be suitably used, and in this case, the same polyolefin or different heteropolyolefin used for the base layer may be used. In particular, in the present invention, the propylene-ethylene copolymer, propylene-butene-1 copolymer, and propylene-ethylene-butene-1 copolymer It is preferable to laminate a propylene-based random copolymer such as a polymer. The preferred structure of the polyolefin-based laminated film of the present invention is as follows: A is a resin composition of a crystalline propylene-based polymer and a low-crystalline or amorphous olefin-based polymer; When the surface layer is represented by C, it can be expressed as follows. (1) AB (2) ABA (3) ABC The overall thickness of the polyolefin-based laminated film of the present invention is 10 to 100 μm, practically 20 to 100 μm. It is preferably in the range of 60 μm. The thickness of each layer is preferably such that the surface layer composed of the resin composition of the crystalline propylene-based polymer and the low-crystalline or amorphous olefin-based polymer has a thickness of 2 to 30 μm, preferably 3 to 30 μm. More preferably, the thickness of the substrate layer is 5 to 70 μm, and 10 to 50 μm.
μm, and the thickness of the other surface layer is preferably 3 to 30 μm. The resin of each layer of the polyolefin laminate film of the present invention may contain additives such as an antioxidant, a lubricant, an antiblocking agent, an antistatic agent and an antifogging agent, if necessary, to inhibit the effects of the present invention. It can be added within a range that does not occur. As a method for producing the polyolefin-based laminated film of the present invention, a known method can be applied. In particular, a co-extrusion molding method, an extrusion lamination method and the like are used. When the polyolefin-based laminated film of the present invention is manufactured by a co-extrusion molding method, the crystalline polyolefin is used for the base material layer, the resin composition specified in the present invention is used for the surface layer, and the base material layer may be used, if necessary. Can be produced by a co-extrusion lamination method in which melt extruding is performed using a plurality of extruders and laminated before and after a die or inside a die so that a crystalline polyolefin is laminated on the surface of the die. Although the polyolefin-based laminated film of the present invention may be used as it is, usually, a corona discharge treatment is performed to improve the adhesiveness with the printing ink. The corona discharge treatment is applied to the surface layer composed of the resin composition specified in the present invention. Conditions for Corona Discharge Treatment in the Present Invention
The adhesion between the printing ink of the resulting polyolefin-based laminate film, or from the viewpoint of prevention such as the odor due to damage of the corona discharge treatment, the wetting tension of the film surface
It is performed so as to be 33 to 38 dynes / cm. Ma
Further, a film subjected to a corona discharge treatment used in the present invention
As is clear from the examples described later, the gusset part
The fusing seal strength is 1180 g / 15 mm or more . The polyolefin-based laminated film of the present invention can be used in the production of packaging bags having a gusset shape, and even when corona discharge treatment for improving the surface printability is performed, the gusset portion is blown. No decrease in seal strength
It can be suitably provided as a packaging film. Therefore,
The polyolefin-based laminated film of the present invention can be widely used as a film for wrapping twist bags such as bread and snacks, or a film for wrapping fibers. EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, the following methods were used to measure the wetting tension, MI, crystallinity, molecular weight distribution, fusing seal strength, and printability. 1) Wetting tension was performed according to JIS K6768. 2) The measurement was carried out according to MI JIS K7210. 3) Measurement of crystallinity The X-ray output was measured using an X-ray diffractometer manufactured by JEOL Ltd.
kw (tube voltage: 40 kv, tube current: 400 mA), target: Cu, measurement angle: 2θ = 9 to 31 degrees. The crystal peak was waveform-separated from the obtained X-ray diffraction pattern, and the crystallinity was determined from the area intensity ratio. The sample is
What was previously melted at 230 ° C. and then gradually cooled to 50 ° C. was used. 4) Measurement of molecular weight distribution Using a water permeation type 150C gel permeation chromatography (GPC), orthodichlorobenzene (ODCB) as an eluent, and a column GMH6H
T (manufactured by Tosoh Corporation). The molecular weight distribution (Mw / Mn) was determined from the ratio of the obtained weight average molecular weight (Mw) and number average molecular weight (Mn). 5) Measurement of Fusing Seal Strength A gusset-containing packaging bag was made using a PP500 bag making machine manufactured by Kyoei Printing Machinery. A gusset seal portion at the time of bag making at a sealing temperature of 320 ° C. and a bag making speed of 140 sheets / minute was cut out, and a tensile speed of 100 mm / min. The seal strength (indicated by g / 15 mm width) when peeled off was determined. 6) Evaluation of printability Gravure ink "Alpha RG" (manufactured by Toka Pigment Chemical Co., Ltd.) was applied to the corona discharge treated surface of the film with a bar coater # 10.
After applying using No. 0, it was dried at 80 ° C. for 1 minute. Cellophane tape (Nichiban cellophane tape)
Was affixed, and a five-step evaluation was performed from the remaining area of the printing ink in the case where the printing ink was more rapidly peeled off. Peeling area: 0%: more than 50% and less than 5%: more than 45% and less than 20%: 3 more than 20% and less than 50%: more than 250%: 1 (evaluation is 4 or more; <Example 1> Crystalline propylene-ethylene copolymer (ethylene content = 4.2 mol%, MI =
(0.5 g / 10 min) 100 parts by weight, 0.13 parts by weight of 1,3-bis- (t-butylperoxyisopropyl) benzene as a radical generator, and pentaerythrityl-tetrakis as an antioxidant [3- (3,5-
0.1 parts by weight of di-t-butyl-4-hydroxyphenyl) propionate and tris (2,4-di-t-
Butylphenyl) phosphite 0.1 part by weight, calcium stearate 0.1 part by weight as a chlorine scavenger, erucamide amide 0.15 part by weight as a lubricant, and silica 0.3 part by weight as an antiblocking agent were mixed. And kneading and heating at a temperature of 190 ° C. The resulting modified propylene-ethylene copolymer had a crystallinity of 56.8%, an MI of 27.4 g / 10 min, and a molecular weight distribution of 2.7. The modified propylene thus obtained is
90 parts by weight of ethylene copolymer and 10 parts by weight of low crystalline ethylene-butene-1 copolymer (butene-1 content = 12 mol%, crystallinity = about 5%, MI = 7 g / 10 min) Were mixed to prepare a resin composition (A). Using three extruders, the surface layer was the resin composition (A), and the substrate layer was the crystalline propylene homopolymer (B) (crystallinity = 56.7).
%, MI = 8.5 g / 10 min), propylene-ethylene-butene-1 copolymer (C) whose other surface layer is crystalline (crystallinity = 57.2%, MI = 7 g / 10 min, (Ethylene content = 3.7 mol%, butene-1 content = 3.5 mol%), and extruded so that the composition ratio A: B: C was 1: 2: 1, and 3 types of 3 having a thickness of 30 μm. A laminated film of layers was obtained. Further, the surface of the obtained laminated film on the surface layer (A) side was subjected to a corona discharge treatment,
After time aging, a gazette bag test was performed. The fusing seal strength of the gusset part is 1630g / 15m
m, which was sufficient for practical use. The wet tension of the obtained laminated film was 35 dynes / c.
m, and the printability was also evaluated as 5, which was excellent without ink bleeding. Examples 2 to 7 As shown in Table 1, the crystalline propylene before kneading and heating was
A predetermined amount of 100 parts by weight of the ethylene copolymer (a) and a radical generator were mixed, and further, other additives were mixed in the same manner as in Example 1. Thereafter, the mixture was kneaded and heated at 190 ° C. with an extruder to obtain a resin. 1 to 5 were obtained. The MI and molecular weight distribution of the obtained crystalline modified propylene-ethylene copolymer are shown in column b of Table 1. Resins 1 to 5 and a low crystalline or amorphous olefin polymer were mixed at the ratio shown in Table 2 to obtain a resin composition (A). As in Example 1, this resin composition (A) is used for the surface layer, and the base layer (B) and the other surface layer (C) are each laminated using the same resin as in Example 1, and three types of three layers are laminated. A film was obtained. The composition ratio A: B: C is 1: 2: 1, and the total thickness is 3
It was set to 0 μm. The surface of the obtained laminated film on the side of the surface layer (A) was subjected to corona discharge treatment, aged at 40 ° C. for 24 hours, and then subjected to gusset sealing, and the fusing seal strength and printability of the gusset portion were evaluated. . The results are shown in Table 2. All exhibited excellent fusing seal strength and printability. Example 8 Example 1 was repeated except that a crystalline propylene homopolymer (MI = 1.0 g / 10 min) was used instead of the crystalline propylene-ethylene copolymer of Example 1. A modified propylene homopolymer was obtained in the same manner as described above. The resulting modified propylene homopolymer has a crystallinity of 5
9.2%, MI was 25.0 g / 10 min, and molecular weight distribution was 2.8. Except for using this modified propylene homopolymer, a three-layer three-layer film was obtained in the same manner as in Example 1. The wetting tension on the surface of the obtained laminated film is 3
The gusset part had a fusing seal strength of 1390 g / 15 mm and a printability rating of 5. <Examples 9 to 11> In the same manner as in Example 1, the thicknesses of the surface layer, the base material layer and the other surface layers were as shown in Table 3.
To obtain a laminated film of three types and three layers. Further, the surface layer (A) side of the obtained laminated film was subjected to a corona discharge treatment, aged at 40 ° C. for 24 hours, and then subjected to a gusset bag test. Table 3 also shows the fusing seal strength of the gusset portion of the obtained laminated film and the printability evaluation results. All of them exhibited a fusing seal strength enough to withstand practical use and good printability. Example 12 In Example 1, a linear low-density polyethylene copolymer (B) (crystallinity: 37.9%, density: 0.912 g / cm ³ , copolymer component) (Hexene-1; 4.5 mol%) except that coextrusion was carried out using three extruders in the same manner as in Example 1,
Layer composition ratio A: B: C is 1: 2: 1 and 30 μm 3 types 3
A laminated film of layers was obtained. After the surface layer (A) was subjected to corona discharge treatment and aged at 40 ° C. for 24 hours, the same evaluation as in Example 1 was performed. The value of the fusing seal strength of the gusset part was 1470 g / 15 mm, the wettability index of the film surface was 35 dynes / cm, and the printability was evaluated as 5, which was excellent without ink dropping. Comparative Example 1 Modified propylene of Example 1
Instead of the ethylene copolymer, a crystalline propylene-ethylene copolymer having a crystallinity of 52.7%, a molecular weight distribution of 4.8, an MI of 8 g / 10 min, and an ethylene content of 5.0 mol% was used. Otherwise, in the same manner as in Example 1, a three-layer three-layer laminated film was obtained. The printability of the obtained laminated film was 5, which was satisfactory, but the fusing seal strength of the gusset portion was a low value of 820 g / 15 mm, which was a problematic value in practical use. <Comparative Examples 2 to 4> Three kinds of three layers were prepared in the same manner as in Example 1 except that the modified propylene-ethylene copolymer of Example 1 was replaced with resins 6 to 8 shown in Table 1. A laminated film was obtained. The evaluation results of the obtained laminated film are shown in Comparative Examples 2 to 4 in Table 2. In all cases, the printability was excellent, but the fusing seal strength at the gusset portion was low and insufficient. [Table 1] [Table 2] [Table 3]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-234447 (JP, A) JP-A-59-75934 (JP, A) JP-A-8-259752 (JP, A) JP-A-61-24 23634 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 C08L 23/00-23/36 C08J 5/18

Claims (1)

(57) Claims 1. A crystal having a molecular weight distribution (Mw / Mn) of 2.5 to 4.0 represented by a ratio of a weight average molecular weight (Mw) to a number average molecular weight (Mn). and 99 percent by weight sex propylene polymer 50, a layer of resin composition comprising to 1 wt% and no low-crystalline or amorphous olefinic polymer 50 on at least one surface layer, the surface layer is corona Discharge treatment
With a wet tension of 33-38 dynes and a gusset
The part fusing seal strength must be 1180 g / 15 mm or more.
And a polyolefin-based laminated film.