JP3401745B2 - Soft polyolefin film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel soft polyolefin film. Specifically, it is a flexible polyolefin film having excellent anti-fogging property and not causing whitening in appearance over a long period of time, which is suitable as a film for stretch packaging.

[0002]

2. Description of the Related Art Conventionally, a polyolefin resin polymerized by using a Ziegler-Natta catalyst or the like has a trace amount of a catalyst residue containing halogens represented by chlorine, that is, a halogen-containing catalyst residue in the resin. Since the above-mentioned halogen-containing catalyst residue is likely to exist in the amorphous part, the soft polyolefin resin containing a large amount of the amorphous part has a higher probability of having the catalyst residue in the resin than the highly crystalline polyolefin resin. The halogen in the residue impairs the stability of the resin, and when it comes into contact with a peripheral material such as a metal, it may cause corrosion such as rust.

Therefore, in order to stabilize the resin, to have a rust preventive effect and a slipping effect, industrially, a metal salt of a higher saturated fatty acid represented by calcium stearate is added, and halogen is used as a fatty acid residue. It has been generally practiced to capture halogen in the resin by the esterification action of substituting into the.

On the other hand, there has been proposed an anti-fog film in which a liquid anti-fog agent is added in order to give the above film a quick-acting anti-fog property.

However, the soft polyolefin film using the above metal salt of higher saturated fatty acid as the chlorine scavenger has a problem that not only the effect of adding the liquid antifogging agent is poor but also the film surface is whitened.

[0006]

Therefore, it has been a major subject to develop a film comprising a soft polyolefin resin containing a halogen-containing catalyst residue, in which the effect of a liquid antifogging agent can be sufficiently exerted and which has no problem of whitening. .

[0007]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies in view of the above problems. As a result, free stearic acid resulting from specific saturated fatty acid salts such as calcium stearate and esters, which have been conventionally added to soft polyolefin resins as chlorine scavengers or lubricants, significantly impair the effects of the above liquid anti-fog agents. Moreover, it was found that the surface whitening occurs. As a result of further research based on such findings, the amount of free stearic acid present in the resin composition was substantially reduced by using hydrotalcites as a chlorine scavenger in a soft polyolefin resin containing a halogen-containing catalyst residue. Found to be able to obtain a film in which the above problems have been solved by forming the above composition by using it together with a liquid antifogging agent.
The present invention has been completed.

That is, according to the present invention, 100 parts by weight of a soft polyolefin resin containing a halogen-containing catalyst residue, 0.01 to 2 parts by weight of hydrotalcites, and 0.1 to 2 parts of a liquid antifogging agent.
Ri Do from the composition of 10 parts by weight, and, put in the composition
The content of free saturated fatty acid having 15 to 36 carbon atoms is 0.0
It is a soft polyolefin film of 7% by weight or less .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A soft polyolefin resin containing a halogen-containing catalyst residue used in the present invention is usually
Propylene homopolymerized in the gas phase or liquid phase in the presence of a halogen-containing transition metal catalyst represented by Ziegler-Natta catalyst, or gas phase of propylene and ethylene or α-olefin having 4 to 20 carbon atoms Alternatively, they collectively refer to those that can be obtained by copolymerization in a liquid phase.

In the present invention, all the resins corresponding to the above can be used, but when the soft polyolefin film of the present invention is used as a stretch packaging film, a soft polyolefin resin containing the following halogen-containing catalyst residue is preferable. Is.

The soft polyolefin resin containing the above halogen-containing catalyst residue comprises: a) a propylene-based polymer having a propylene-based monomer unit content of 97 mol% or more.
70% by weight, b) Propylene-ethylene random copolymer having a propylene-based monomer unit content of 40 to 95 mol% and an ethylene-based monomer unit content of 60 to 5 mol%. It is composed of 95 to 30% by weight.

The above-mentioned a) propylene-based polymer has a propylene-based monomer unit content of 97 mol% or more. Specific examples thereof include a propylene homopolymer and a random copolymer of 97 mol% or more of propylene and 3 mol% or less of another monomer copolymerizable with the propylene.
Here, as the other monomer, ethylene, 1-butene, 3
Α-olefins having 2 to 12 carbon atoms such as -methylbutene, 4-methyl-1-pentene and 1-hexene are preferable,
Ethylene is particularly preferable.

These propylene-based polymers can be usually obtained by polymerizing in a gas phase or a liquid phase in the presence of a halogen-containing transition metal catalyst represented by a Ziegler-Natta catalyst. If the content of the propylene-based monomer unit is less than 97 mol%, the resulting film is not sufficiently cut, and the tightening force at the time of packaging cannot be obtained, which is not preferable.

In the above-mentioned b) propylene-ethylene random copolymer, the content of propylene-based monomer units is 40 to 95 mol%, preferably 50 to 80 mol%, and the ethylene-based monomer is used. The content of the unit is 60 to 5 mol%, preferably 50 to 20 mol%. Here, when the content of the propylene-based monomer unit is less than 40 mol%, the transparency is lowered and the self-adhesiveness is too high, so that blocking occurs at the time of unwinding the film.
When it exceeds 5 mol%, flexibility, stretchability and self-adhesiveness are not sufficient, which is not preferable.

These b) propylene-ethylene random copolymers are usually obtained by polymerizing in a gas phase or a liquid phase in the presence of a transition metal catalyst containing a halogen represented by a Ziegler-Natta catalyst. it can.

The MI of the soft polyolefin resin at 230 ° C. is preferably 0.1 to 20 g / 10 min. M
When I is in the above range, the deterioration of the film appearance and the transparency due to the occurrence of surface roughness during film formation is particularly small, and the strength of the film is not significantly decreased, which is preferable.

The compounding ratio of a) propylene-based polymer and b) propylene-ethylene random copolymer is a) propylene-based polymer 5 to 70% by weight, preferably 6 to 60% by weight,
b) Propylene-ethylene random copolymer 95-30
%, Preferably 94-40% by weight.

Here, when the content of a) propylene-based polymer is less than 5% by weight, that is, when the content of b) propylene-ethylene random copolymer exceeds 95% by weight,
When the tightening force and the cuttability at the time of packaging are insufficient and a) the content of the propylene-based polymer exceeds 70% by weight, that is, b) the content of the propylene-ethylene random copolymer is less than 30% by weight. Inadequate stretchability, self-adhesiveness, and flexibility.

The a) propylene polymer and the b) propylene-ethylene random copolymer may be blended mechanically, but some or all of them may be blended with a block copolymer. It may be microblended. Particularly, from the viewpoint of improving the transparency of the obtained soft polyolefin film, a) the propylene-based polymer accounts for 10 to 80% by weight in the component, and the block copolymerization weight with the b) propylene-ethylene random copolymer is a). It is preferably blended as a united body.

At this time, the propylene-ethylene block copolymer may be obtained by any known method. Specifically, in the first-stage polymerization, as described in Japanese Patent Publication No. 7-53771, first, in the presence of a halogen-containing titanium compound and an aluminum compound,
It is preferable that a propylene-based polymer containing a halogen-containing titanium compound is produced, and then, in the second-stage polymerization, propylene and ethylene are copolymerized in the presence of the propylene-based polymer.

In the present invention, hydrotalcites are
It is effective as a chlorine scavenger containing no free saturated fatty acid, and when combined with a liquid antifogging agent, it effectively exerts an antifogging effect on the film and prevents whitening over time.

As the above-mentioned hydrotalcites, those having a function as a chlorine scavenger can be used without particular limitation.
That is, known natural products, synthetic products, and the like are used, and synthetic products containing few impurities are preferably used.

Hydrotalcites are represented by the following general formulas (1) and (2) M _X Al _y (OH) _{2 (x-1) + 3y} · CO ₃ · nH ₂ O (1) M _X Al _y (OH) _{2 (x-1) + 3y} · HPO ₄ · nH ₂ O (2) (where M is one or more divalent metal atoms, and x and y
Is a positive number and n is a number of 0 or more. ).

The divalent metal atom represented by M in the above formulas (1) and (2) is selected from, for example, Group A metal atoms and Group B metal atoms of the Periodic Table, and among them, magnesium and calcium. Hydrotalcites composed of zinc and zinc atoms are generally used. Two or more kinds of these metal atoms may be contained in one molecule. Specifically, for example, Mg ₆ Al ₂ (OH) ₁₆ · CO ₃ · 4H ₂ O Mg _4.5 Al ₂ (OH) ₁₃ · CO ₃ · 3.5H ₂ O Ca ₆ Al ₂ (OH) ₁₆ · CO ₃ · _{4H 2 O Zn 6 Al 2 (} OH) 16 · CO 3 · 4H 2 O Mg 3 ZnAl 2 (OH) 12 · CO 3 · 4H 2 O is preferably exemplified.

The blending amount of the above-mentioned hydrotalcites is 0.01 to 2 parts by weight, preferably 0.04 to 1.5 parts by weight, based on 100 parts by weight of the polyolefin resin. If the blending amount is 0.01 parts by weight or less, the halogen scavenging ability is insufficient because the resin is not sufficiently dispersed in the resin. Compounding amount is 2
When the amount is more than the weight part, transparency is lowered by bleeding by itself, which is not preferable.

Regarding the particle size of the above-mentioned hydrotalcites, when the average particle size is the primary particle or the secondary particle size,
Those having a thickness of 0.01 to 15 μm, preferably 0.05 to 8 μm are suitably used. When the particle size is within this range, dispersibility is preferable and, further, stretchability for a stretch film is sufficient, which is preferable.

The liquid antifogging agent used in the present invention is
Known substances existing in a liquid state at room temperature can be used without particular limitation. Typical examples include polyglycerin fatty acid ester, sorbitan fatty acid ester, ethylene oxide adduct, and aliphatic amine, and at least one selected from these is used. Specific examples of these liquid antifogging agents include polyglycerin and fatty acid of 1: 1 to 1: 4 as the polyglycerin fatty acid ester.
The main component is a compound obtained by an esterification reaction by a conventional method and in which a part of the hydroxyl groups of polyglycerin is ester-bonded with a fatty acid. As the polyglycerin, polyglycerin having a degree of polymerization n = 1 to 10 such as monoglycerin, diglycerin and triglycerin can be used, but polyglycerin having a degree of polymerization n = 1 to 4 is preferable in terms of antifogging property and economical efficiency. . Examples of the fatty acid forming the ester include those having 8 to 18 carbon atoms such as lauric acid and myristic acid and oleic acid, and these can be used alone or as a mixture of two or more kinds. Among them, carbon number 15 to 3
Those containing substantially no free saturated fatty acid of 6 are preferred, and unsaturated fatty acids having 14 or less carbon atoms such as lauric acid and unsaturated fatty acids such as oleic acid, either alone or as a mixture, are particularly preferred.

The sorbitan fatty acid ester is obtained by an esterification reaction of sorbitol and a fatty acid in a molar ratio of 1: 1 to 1: 2 by a conventional method, and is mainly composed of sorbitan monofatty acid ester and / or sorbitan difatty acid ester. And Examples of the fatty acid forming the ester include those having 8 to 18 carbon atoms such as lauric acid, myristic acid and oleic acid, and these can be used alone or as a mixture of two or more kinds. Among them, carbon number 15 to 3
Those containing substantially no free saturated fatty acid of 6 are preferred, and unsaturated fatty acids having 14 or less carbon atoms such as lauric acid and unsaturated fatty acids such as oleic acid, either alone or as a mixture, are particularly preferred.

The ethylene oxide adduct is preferably an ethylene oxide adduct of a higher alcohol, an ethylene oxide adduct of an alkylphenol or an ester compound with polyethylene glycol.

Examples of the aliphatic amine include polyoxyethylene alkylamine and ethanol alkylamine, and examples of the alkyl group include those having 7 to 17 carbon atoms such as lauryl group, myristyl group and oleyl group.
A lauryl group and an oleyl group are preferred.

In the present invention, the liquid antifogging agent is blended in a soft polyolefin resin 1 containing a halogen-containing catalyst residue.
It is 0.1 to 10 parts by weight, preferably 0.2 to 9 parts by weight with respect to 00 parts by weight. When the blending amount is 0.1 parts by weight or less, the antifogging property is not sufficiently exhibited due to the small amount, and when the blending amount is 10 parts by weight or more, the slipperiness is too large and the anti-fogging property is low. It is not sufficient because slippage occurs, the film-forming property is inferior, and the bleeding amount of the antifogging agent is too large, so that the antifogging effect decreases.

In the present invention, it is possible to substantially eliminate the amount of free saturated fatty acid having 15 to 36 carbon atoms by combining the soft polyolefin with the hydrotalcite and the liquid antifogging agent. Depending on the type of the liquid antifogging agent, there may be a small amount of free saturated fatty acid having 15 to 36 carbon atoms. Further, even when other optional additives such as a lubricant are added, the free saturated fatty acid may be present.

In the present invention, such carbon number 1
In order to prevent problems due to free saturated fatty acids of 5 to 36, the carbon number of the free saturated fatty acids in the composition is 0.07% by weight or less, preferably 0.05% by weight or less.
Restrict. Thereby, the antifogging effect of the film by the liquid antifogging agent can be sufficiently exhibited, and the whitening of the film over time can be effectively prevented.

Of the above free saturated fatty acids, free stearic acid has a strong anti-fogging property, and the amount of the free stearic acid present is preferably 0.02% by weight or less based on the composition.

In the present invention, in order to impart various properties to the composition constituting the above-mentioned soft polyolefin film, within the range where the above conditions are satisfied and within the range where the effects of the present invention are not significantly impaired. Various additives may be added.

Examples of such additives include weathering agents such as antioxidants and ultraviolet absorbers, lubricants, antiblocking agents, adhesives, matting agents, antistatic agents, oxygen and carbon dioxide gas absorbents, and freshness-retaining agents. Examples include agents, deodorants, fragrances, antibacterial agents, and the like.

The soft polyolefin resin containing the halogen-containing catalyst residue may be molded into a film by any known molding method. Specifically, the extrusion casting method,
The upward inflation method, the downward water cooling inflation method, the biaxial tenter method, the tubular biaxial stretching method and the like can be used without any limitation. The film thus obtained may be unstretched or may be uniaxially or biaxially stretched after the film formation, but the stretching ratio is preferably in the range of 40 times or less in terms of area ratio. .

In the present invention, in order to further improve transparency and flexibility, at least one surface of the soft polyolefin film made of the above polyolefin composition,
The content of ethylene-based monomer units is 98 to 90 mol%, and the content of vinyl acetate-based monomer units is 2
It is preferable to laminate a layer comprising an ethylene-vinyl acetate copolymer in an amount of 10 mol%. Where ethylene-
When the content of the vinyl acetate-based monomer unit of the vinyl acetate copolymer is less than 2 mol%, the transparency, flexibility and stretchability are insufficient, and the content of the vinyl acetate-based monomer unit is insufficient. If it exceeds 10 mol%, the cuttability is insufficient, and the self-adhesiveness is too high, so that blocking is likely to occur during unwinding of the film, which is not preferable.

19 of the above ethylene-vinyl acetate copolymer
MI at 0 ° C. is preferably 0.1 to 20 g / 10 min. When the MI is in the above range, the appearance of the film is not deteriorated and the transparency is not deteriorated due to the occurrence of surface roughness during the film formation, and the strength of the film is not significantly decreased, which is preferable.

In the present invention, the surface layer made of the above-mentioned ethylene-vinyl acetate copolymer may be added with additives in order to impart various properties to the film within a range that does not significantly impair the effects of the present invention. good. For example, antioxidants, weathering agents such as UV absorbers, anti-blocking agents, adhesives, matting agents, antistatic agents, absorbers of oxygen and carbon dioxide,
Examples include freshness-retaining agents, deodorants, fragrances, antibacterial agents, and the like.

As a method for laminating the surface layer comprising the ethylene-vinyl acetate copolymer on the soft polyolefin film, any known laminating method may be used, but the laminating method by coextrusion is generally used. is there.

The thickness of the soft polyolefin film is not particularly limited, and a thick film called a sheet is included in the category of the film in the present invention, but is generally 5 to 200 μm, preferably 5 to 50 μm. . Further, in the case of a laminated soft polyolefin film in which a surface layer made of an ethylene-vinyl acetate copolymer is laminated on at least one surface of the soft polyolefin film, the total thickness of the film is generally 5 to 200 μm, preferably 5 to 50 μm. And the thickness of the surface layer is 5 times the thickness of the base layer made of the soft polyolefin film.
It is preferably 0% or less from the viewpoint of cuttability.

[0043]

EFFECT OF THE INVENTION The soft polyolefin film of the present invention has an excellent anti-fogging effect which is excellent in quick-acting property, and further has an excellent property that appearance whitening does not occur after aging. Therefore, it can be sufficiently and effectively used as a stretch packaging film.

[0044]

EXAMPLES Examples will be shown below to more specifically describe the present invention, but the present invention is not limited to these examples.

The MI polyolefin resin was measured according to JIS-K7210. On the other hand, ethylene-vinyl acetate copolymer is JIS-
It measured according to K6730.

Haze It was measured according to JIS-K7105.

Appearance The appearance of the whitened film was visually observed immediately after film formation and after storage at 40 ° C. for 1 week, and evaluated on a three-point scale.

⊚: No whitening ○: Slight whitening ×: Significant whitening Also, the haze value of the film was measured immediately after film formation, after storage at 40 ° C. for 1 week, and the change value was measured by the formula of Formula 1.

[0049]

[Equation 1]

After placing 50 ml of distilled water in a 100 ml beaker having an antifogging property, the beaker was covered with the soft polyolefin film, and the beaker was left at 0 ° C. for 12 hours.

◎: Good without water droplets ○: Slight water droplet adhesion ×: Poor due to remarkable water droplet adhesion Stretchability Teraoka Seiko Co., Ltd., automatic stretch wrapping machine AW3600
A film having a width of 300 mm was stretched 100% by using, and the stretchability of the film was evaluated in two stages.

◯: No breakage occurs during stretching X: Cut property that the film breaks during stretching Teraoka Seiko Co., Ltd. automatic stretch wrapping machine AW3600
Was used to evaluate whether or not the film could be cut with a serrated blade in an automatic wrapping machine in three levels.

⊚: Good cutting is possible and the cut surface is smooth.

◯: It is possible to cut, but the cut end is not smooth.

X: Insufficient cuttability.

A feeling of finish Teraoka Seiko Co., Ltd., automatic stretch wrapping machine AW3600
After packaging 4 pieces of mandarin orange C-65 foam tray with a film having a width of 300 mm, the tension of the film in which the tray was packaged was evaluated in 3 stages.

⊚: A film wrapping the tray is stretched,
It is tight.

◯: Wrinkles are partially generated on the film in which the tray is wrapped, and the tightening force is reduced.

X: Wrinkles were generated in the film in which the tray was wrapped, and the film was not tightened.

Analysis of Free Stearic Acid Since free stearic acid is soluble in chloroform / acetone, free stearic acid in the soft polyolefin resin was quantitatively analyzed by measuring free stearic acid in chloroform / acetone by GC. Specifically, 5 g of the soft polyolefin resin was Soxhlet-extracted with 100 cc of chloroform, then dropped into 200 cc of cold acetone and cooled to 0 ° C. to precipitate low molecular weight components and other additives. Then, the chloroform / acetone solution was filtered, and the filtrate was concentrated to 10 CC to prepare a sample, which was subjected to GC measurement. The standard samples for quantification are 100, 500 and 10
A 00 ppm-stearic acid / acetone standard solution was used.

The resins, hydrotalcites and liquid antifogging agents used in the present invention are shown below.

P1: propylene homopolymer (MI2.
R1; propylene-ethylene random copolymer (content of ethylene-based monomer unit: 2.0 mol%, MI
R2; propylene-ethylene random copolymer (content of ethylene-based monomer units is 23 mol%, MI1.
R3; propylene-ethylene random copolymer (content of ethylene-based monomer units is 35 mol%, MI1.
5 g / 10 min) B1; propylene-ethylene block copolymer (propylene homopolymer part 7% by weight, propylene-ethylene random copolymer part 93% by weight with a content of monomer units based on ethylene of 23 mol%, MI 1.5 g / 10 min) B2; propylene-ethylene block copolymer (18% by weight of propylene homopolymer part, 82% by weight of propylene-ethylene random copolymer part with content of ethylene-based monomer unit of 35 mol%) %, MI 1.6 g / 10 mi
n) .V1; ethylene-vinyl acetate copolymer (content of vinyl acetate-based monomer unit is 5.8 mol%, MI is 2.7 g)
/ 10 min) V2; ethylene-vinyl acetate copolymer (content of vinyl acetate-based monomer unit 8.9 mol%, MI 1.0 g)
/ 10 min) Hydrotalcites / Mg _4.5 Al ₂ (OH) ₁₃ / CO ₃ / 3.5H ₂ O (molecular weight 510, average particle size 5.7 μm) Liquid anti-fog component / polyoxyethylene lauryl ether (HLB = 1
0.6) -Polyglycerin monolaurate (HLB = 7.1) -Polyglycerin sesquioleate (HLB = 5.0) -Diethanol laurylamine (HLB = 6.1) Examples 1-10, 13, 14 Comparative Examples 1 to 5 A soft polyolefin resin containing a halogen-containing catalyst residue shown in Table 1, a hydrotalcite, and a liquid antifogging agent were melt-kneaded in a twin-screw melt-kneading extruder with a composition shown in Table 2 to form a pellet resin. A composition was obtained. This resin composition was extruded into a ring die using a single screw extruder and extruded into a film at 220 ° C. Next, air is blown into the molten cylindrical film, and 10 ° C. air is blown in a ring shape from the outside,
The mixture was air-cooled and solidified, and was drawn at a draft ratio of 30, a blow ratio of 6 and a take-up speed of 30 m / min to obtain a single layer film having a thickness of 13 μm. The results of measuring the physical properties of the obtained film are shown in Tables 2, 3 and 4.

Examples 11 and 12 A three-layer inflation die was used. This inner surface layer,
The ethylene-vinyl acetate copolymer was extruded at 160 ° C. from the inner surface layer and outer surface layer extruder so that the extrusion rate of the base material layer and outer surface layer was 1: 4: 1. A soft polyolefin composition containing a halogen-containing catalyst residue having the composition shown in Table 1 was extruded at 180 ° C. Next, air is blown into the molten cylindrical film, and 10 ° C. air is blown from the outside in a ring shape to solidify by air cooling, and the draft ratio is 30, the blow ratio is 6, and the take-up speed is 30 m / min. I got a film. The results of measuring the physical properties of the obtained film are shown in Table 2.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

[Table 4]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B65D 65/40 B65D 65/40 A C08L 23/10 C08L 23/10 (56) References JP 62-179530 (JP, A) ) JP-A-6-136179 (JP, A) JP-A-1-202446 (JP, A) JP-A-10-67882 (JP, A) JP-B-59-30737 (JP, B1) (58) Field (Int.Cl. ⁷ , DB name) C08J 5/18 B32B 27/18 B32B 27/20 B32B 27/28 B32B 27/32 B65D 65/40 C08L 23/10

Claims (6)

(57) [Claims] 1. 100 parts by weight of a soft polyolefin resin containing a halogen-containing catalyst residue, 0.0 hydrotalcites
1-2 parts by weight, and liquid antifogging agents Ri Do from the composition of from 0.1 to 10 parts by weight, and, 15 to the number of carbon atoms in the composition
36 free saturated fatty acid content of 0.07 wt% or less
A soft polyolefin film. 2. A composition comprising free stearic acid in a composition.
The soft porosity according to claim 1, wherein the content is 0.02% by weight or less.
Liolefin film . 3. The soft polyolefin resin comprises 5 to 70% by weight of a) a propylene-based polymer in which a) the content of propylene-based monomer units is 97 mol% or more, and b) the content of propylene-based monomer units. Is 40 to 95 mol%,
Content of monomer unit based on ethylene is 60 to 5 mol%
Propylene-ethylene random copolymer 95-3
The soft polyolefin film according to claim 1, which comprises 0% by weight. 4. A stretch wrapping film comprising the soft polyolefin film according to claim 1. 5. The content of the monomer unit based on ethylene is 98 to 90 mol%, and the content of the monomer unit based on vinyl acetate is on at least one surface of the soft polyolefin film according to claim 1. Of the ethylene-vinyl acetate copolymer having a content of 2 to 10 mol% is a laminated soft polyolefin film. 6. A stretch packaging film comprising the laminated soft polyolefin film according to claim 5.