TWI878309B - Stretch wrap film - Google Patents

Abstract

One aspect of the present invention is a stretch wrap film comprising a polyvinyl chloride resin, a plasticizer and a blue colorant, wherein the mass ratio of the plasticizer content to the blue colorant content is 30 or more.

Description

Stretch packaging film

The present invention relates to a stretch packaging film.

Stretch wrapping films are used, for example, in supermarkets to wrap fresh foods and other foods by stretch wrapping equipment. Among them, various studies have been conducted on stretch wrapping films containing plasticizers in polyvinyl chloride resins. As such a stretch wrapping film, for example, Patent Document 1 discloses a stretch wrapping film as follows: a layer (A) containing a vinyl chloride resin composition is arranged as the outermost layer, and the vinyl chloride resin composition constituting the (A) layer is prepared by mixing 1 to 70 parts by mass of a plasticizer in 100 parts by mass of the vinyl chloride resin. [Prior art document] [Patent document]

[Patent Document 1] Japanese Patent Publication No. 2008-213340

[Problems to be solved by the invention] However, since stretch wrap films are used for food as described above, it is required that they can be easily identified even when fragments of the stretch wrap films are mixed into the food. In contrast, it is believed that the stretch wrap films can be easily identified by coloring them blue by containing a blue coloring agent. However, according to the research of the inventors and others, it was found that the properties required for the stretch wrap films, such as stretchability, releasability, and extraction properties, may not be good when the conventional stretch wrap films only contain a blue coloring agent.

Therefore, the present invention is made in view of the above situation, and its purpose is to provide a stretch packaging film that has excellent stretchability, peelability and extraction properties even if it contains a blue coloring agent. [Means for solving the problem]

The inventors of the present invention have found that by setting the ratio of the content of the plasticizer to the content of the blue coloring agent within a specific range, a stretch packaging film that can take into account stretchability, releasability, and extractability can be formed.

One aspect of the present invention is a stretch wrap film comprising a polyvinyl chloride resin, a plasticizer and a blue colorant, wherein the mass ratio of the plasticizer content to the blue colorant content is 30 or more.

The plasticizer includes a compound represented by the following formula (1), and the mass ratio of the content of the compound represented by the following formula (1) to the content of the blue coloring agent may be 20 or more. [Chemical 1] In formula (1), ^R1 and ^R2 each independently represent an alkyl group.

In formula (1), ^R1 may be an alkyl group having 9 carbon atoms.

^R2 in formula (1) may be an alkyl group having 9 carbon atoms.

The mass ratio of the content of the compound in which ^R1 and ^R2 are alkyl groups having 9 carbon atoms to the content of the blue coloring agent in formula (1) can be 15 or more. [Effects of the Invention]

According to the present invention, a stretch packaging film having excellent stretchability, releasability and extractability can be provided even when containing a blue coloring agent.

A stretch wrap film (hereinafter also referred to as "film") according to one embodiment contains a polyvinyl chloride resin, a plasticizer, and a blue coloring agent.

The so-called "stretch wrapping film" is a film used for stretch wrapping (packaging performed by a stretch wrapping device). Typical examples of stretch wrapping films include: pre-packaging stretch wrapping films for placing fruits and vegetables, lean meat, cooked food, etc. on a pallet (e.g., a lightweight pallet) and overlapping them; packaging films that are overlapped to secure the goods during transportation, etc.

(Polyvinyl chloride resin) From the viewpoint of excellent mechanical properties, polyvinyl chloride resin may be a homopolymer of vinyl chloride (polyvinyl chloride resin), or for the purpose of imparting other properties, a copolymer of vinyl chloride and other monomers copolymerizable therewith. The copolymer may be a graft copolymer, a block copolymer, or a random copolymer. Examples of other monomers include: olefins such as ethylene, propylene, and butene; vinyl esters of saturated acids such as vinyl acetate and vinyl laurate; alkyl esters of unsaturated acids such as methyl acrylate and methyl methacrylate; alkyl vinyl ethers such as lauryl vinyl ether; maleic acid, acrylonitrile, styrene, methyl styrene, vinylidene fluoride, etc.

When the polyvinyl chloride resin is a copolymer, the content of the vinyl chloride unit in the copolymer may be 10% by mass or more based on the total monomer unit, preferably 30% by mass or more, and more preferably 50% by mass or more from the viewpoint of excellent mechanical properties. The upper limit of the content of the vinyl chloride unit in the copolymer is not particularly limited, and for example, it may be 99% by mass or less based on the total monomer unit.

The polyvinyl chloride resin may be, for example, a polymer mixture with a three-dimensional polymer of acrylonitrile-butadiene-styrene, a post-processed product obtained by alcohol, or a post-processed product obtained by a chlorine-containing compound. In these cases, the content of the vinyl chloride unit in the polyvinyl chloride resin may be 10% by mass or more based on the total amount of the polyvinyl chloride resin.

From the viewpoint of excellent formability, heat resistance and fluidity of the stretch wrap film, the polyvinyl chloride resin is preferably a polyvinyl chloride resin having an average degree of polymerization of 700 to 1300. The average degree of polymerization in this specification refers to the average degree of polymerization measured in accordance with Japanese Industrial Standards (JIS) K6720-2.

From the viewpoint of excellent productivity, the content of the polyvinyl chloride-based resin can be, for example, 60 mass % or more, 65 mass % or more, or 70 mass % or more, and can be 80 mass % or less, or 75 mass % or less, based on the total amount of the stretch wrap film.

(Plasticizer) As plasticizers, there can be listed: epoxidized oils such as epoxidized linseed oil, epoxidized soybean oil (epoxidized fatty acid glyceride), and epoxidized fatty acid alkyl esters; hydroxy polycarboxylic acid esters such as acetyl tributyl citrate (for example, acetyl tributyl citrate); dibasic acid esters such as adipic acid esters and sebacic acid esters (for example, di-n-butyl sebacic acid); polyol esters such as pentaerythritol esters and diethylene glycol benzoate; phosphoric acid esters such as triphenyl phosphate and tricresyl phosphate; glyceryl diethyl monolaurate; chlorinated wax; polyester plasticizers, etc. From the viewpoint of improving the cold resistance of the film, the plasticizer is preferably a dibasic acid carboxylic acid ester, and more preferably an adipic acid ester. These plasticizers can be used alone or in combination of two or more.

Adipate ester is represented by the following formula (1), for example. That is, the plasticizer preferably contains a compound represented by the following formula (1). In formula (1), ^R1 and ^R2 each independently represent an alkyl group.

The content of the compound represented by the formula (1) relative to 100 parts by mass of the polyvinyl chloride resin (when two or more compounds represented by the formula (1) are included, the total content of these compounds) can be, for example, 10 parts by mass or more or 15 parts by mass or more. From the viewpoint of improving the cold resistance of the film, it is preferably 20 parts by mass or more, more preferably 25 parts by mass or more. From the viewpoint of further improving the stretchability, it is further preferably 27 parts by mass or more. For example, it can be 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less.

^R1 in formula (1) may be a linear alkyl group or a branched alkyl group. ^R1 in formula (1) may be, for example, an alkyl group having 6 to 12 carbon atoms, an alkyl group having 8 or 9 carbon atoms, or an alkyl group having 9 carbon atoms.

^R2 in formula (1) may be a linear alkyl group or a branched alkyl group. ^R2 in formula (1) may be, for example, an alkyl group having 6 to 12 carbon atoms, an alkyl group having 8 or 9 carbon atoms, or an alkyl group having 9 carbon atoms.

Examples of compounds in which ^R1 and ^R2 in formula (1) are alkyl groups having 8 carbon atoms ( ^R1 in formula (1) is an alkyl group having 8 carbon atoms, and ^R2 in formula (1) is an alkyl group having 8 carbon atoms) include dioctyl adipate (bis(2-ethylhexyl) adipate). Examples of compounds in which ^R1 and ^R2 in formula (1) are alkyl groups having 9 carbon atoms ( ^R1 in formula (1) is an alkyl group having 9 carbon atoms, and ^R2 in formula (1) is an alkyl group having 9 carbon atoms) include diisononyl adipate.

The content of the compound in which ^R1 and ^R2 in the formula (1) are alkyl groups having a carbon number of 9 may be, for example, 5 parts by mass or more, 8 parts by mass or more, or 10 parts by mass or more, and is preferably 12 parts by mass or more, and more preferably 15 parts by mass or more, relative to 100 parts by mass of the polyvinyl chloride resin. The content of the compound in which ^R1 and ^R2 in the formula (1) are alkyl groups having a carbon number of 9 may be, for example, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less, relative to 100 parts by mass of the polyvinyl chloride resin.

The total content of the plasticizers may be, for example, 25 or more parts by mass or 30 or more parts by mass relative to 100 parts by mass of the polyvinyl chloride resin. From the viewpoint of improving the cold resistance of the film and further improving the stretchability of the film, it is preferably 35 or more parts by mass, and more preferably 40 or more parts by mass. The total content of the plasticizers may be, for example, 80 or less parts by mass, 70 or less parts by mass, 60 or less parts by mass, or 50 or less parts by mass relative to 100 parts by mass of the polyvinyl chloride resin.

(Blue colorant) The blue colorant is, for example, a colorant whose maximum absorption wavelength in the visible light region (wavelength: the entire region of 380 nm to 750 nm) exists in the range of 600 nm to 750 nm. The absorbance of the blue colorant at the maximum absorption wavelength in the visible light region is preferably two times or more, more preferably three times or more, the absorbance at a wavelength of 470 nm. Specifically, the blue colorant may be copper phthalocyanine (copper phthalocyanine blue), iron (III) hexacyanoferrate (II), a mixture of cobalt oxide and aluminum oxide, indigo or ultramarine. From the viewpoint of further improving strength, dispersibility and solvent resistance, the blue colorant is preferably a blue pigment. The blue coloring agent may be used alone or in combination of two or more.

The content of the blue colorant may be, for example, 0.2 parts by mass or more or 0.5 parts by mass or more relative to 100 parts by mass of the polyvinyl chloride resin, and preferably 1.0 parts by mass or more from the viewpoint of further improving the stretchability of the film. The content of the blue colorant may be, for example, 3.0 parts by mass or less, 2.0 parts by mass or less, or 1.5 parts by mass or less relative to 100 parts by mass of the polyvinyl chloride resin.

In the stretch packaging film of the present embodiment, from the viewpoint of improving the stretchability, releasability and extraction property of the film, the mass ratio (Y1/X1) of the content Y1 of the plasticizer to the content X1 of the blue coloring agent is 30 or more. From the viewpoint of improving the dispersibility of the blue coloring agent, Y1/X1 is preferably 32 or more, more preferably 34 or more. Y1/X1 may be, for example, 50 or less, 45 or less, or 35 or less.

In the stretch wrapping film of the present embodiment, the mass ratio (Y2/X1) of the content of the compound represented by the formula (1) (the total content of the compounds represented by the formula (1) when two or more compounds are included) Y2 to the content of the blue coloring agent X1 may be, for example, 10 or more or 15 or more, and is preferably 20 or more, more preferably 22 or more, or 24 or more, from the viewpoint of improving the cold resistance of the film and further improving the extractability of the film. Y2/X1 may be, for example, 40 or less or 35 or less, and is preferably 33 or less or 30 or less, from the viewpoint of further improving the extractability of the film.

In the stretch wrapping film of the present embodiment, the mass ratio (Y3/X1) of the content Y3 of the plasticizer in which ^R1 and ^R2 are alkyl groups having 9 carbon atoms to the content X1 of the blue coloring agent may be, for example, 6 or more, 9 or more, or 12 or more, and is preferably 15 or more from the viewpoint of improving the cold resistance of the film and further improving the extractability of the film. Y3/X1 may be, for example, 45 or less, 35 or less, 30 or less, or 25 or less, and is preferably 20 or less or 17 or less from the viewpoint of further improving the extractability of the film.

From the viewpoint of particularly improving the stretchability, peelability and extraction properties of the film, the stretch wrapping film preferably satisfies the following conditions of Y1/X1, Y2/X1 and Y3/X1 at the same time. ・Y1/X1 is 30 or more, 32 or more, or 34 or more, and 50 or less, or 45 or less. ・Y2/X1 is 20 or more, 22 or more, or 24 or more, and 33 or less, or 30 or less. ・Y3/X1 is 6 or more, and 20 or less.

From the perspective of maximizing the stretchability, peelability, and extraction properties of the film, the best stretch wrap film is one that satisfies the following Y1/X1, Y2/X1, and Y3/X1 conditions simultaneously. ・Y1/X1 is 30 or more, 32 or more, or 34 or more, and 35 or less. ・Y2/X1 is 20 or more, 22 or more, or 24 or more, and 30 or less. ・Y3/X1 is 12 or more, or 15 or more, and 20 or less, or 17 or less.

Stretch wrapping film contains not only polyvinyl chloride resin, plasticizer and blue coloring agent, but also other ingredients. Other ingredients include: thermoplastic resin other than polyvinyl chloride resin, antifogging agent, stabilizer, lubricant, filler, anti-precipitation agent, antioxidant, mold release agent, viscosity reducer, surfactant, fluorescent agent, surface treatment agent, crosslinking agent, processing aid, adhesive, antistatic agent, ultraviolet absorber, anti-caking agent, etc. When the stretch wrap film contains other components, the content (total content) of the other components may be, for example, 1 part by mass or more and 30 parts by mass or less relative to 100 parts by mass of the polyvinyl chloride-based resin.

The stretch wrap film may include only one layer containing polyvinyl chloride resin, plasticizer and blue colorant, or may include multiple layers. In the case where the stretch wrap film includes multiple layers, the stretch wrap film may include, for example, a first surface layer, an intermediate layer and a second surface layer in sequence. In the above case, for example, the first surface layer and the second surface layer may contain polyvinyl chloride resin, plasticizer and other components added as needed, and the intermediate layer may contain polyvinyl chloride resin, plasticizer, blue colorant and other components added as needed. For example, the stretch wrap film may further include an adhesive layer containing an acid-modified polyolefin resin in order to improve the adhesion between the layers, and may further include a heat-resistant layer containing a polyamide resin in order to improve the heat resistance of the stretch wrap film.

The thickness of the stretch wrap film may be, for example, 5 μm or more or 8 μm or more, and is preferably 10 μm or more from the viewpoint of better suitability as a stretch wrap film. From the viewpoint of excellent operability, the thickness of the stretch wrap film may be preferably 25 μm or less, and more preferably 18 μm or less.

From the viewpoint of excellent visibility, the total light transmittance of the stretch wrap film is preferably 75% or more, more preferably 80% or more, and for example, can be 90% or less. The total light transmittance can be calculated by measuring the incident light amount and the total light transmittance according to JIS K7361-1, and the total light transmittance = (total light transmittance) / (incident light amount) × 100.

The stretch wrapping film is produced, for example, by mixing a polyvinyl chloride resin, a plasticizer, a blue coloring agent, and other components as required by a mixer such as a V-type blender, a belt blender, a Henschel mixer, a high-speed mixer, and kneading the mixture by a mixing roll, a Banbury mixer, a kneader, and the like as required, and then, for example, extruding the mixture to obtain a composition. Specifically, the composition is supplied to the hopper of the extruder, and the target stretch wrapping film is obtained by an inflation method, a T-die method, or the like.

When the stretch wrap film includes multiple layers, the stretch wrap film can be obtained by feeding the constituent materials of each layer into different extruders and performing melt extrusion, and co-extrude and stack the layers by an inflation method, a T-die method, etc. At this time, it is preferred to directly cool the melt extruded from the T-die by a casting roll or the like while drawing it to form the stretch wrap film.

The stretch packaging film obtained in the above manner can be subjected to heat treatments such as longitudinal stretching between heating rollers, various heat fixations, aging, etc., in order to reduce the thermal shrinkage rate, natural shrinkage rate, etc., and to inhibit the occurrence of width shrinkage. It can also be subjected to corona treatment, aging treatment, surface treatment such as printing, coating, etc., in order to improve anti-fogging properties, anti-static properties, adhesion, etc.; surface processing, etc.

Furthermore, the so-called "film" generally refers to a thin, flat product with an extremely small thickness compared to the length and width, with an arbitrary maximum thickness limit, and can be supplied in the form of a roll (refer to Japanese Industrial Standard JIS K6900 as needed), and the so-called "sheet" generally refers to a thin, flat product with a thickness generally smaller than the length and width in the JIS definition. However, the boundary between sheets and films is not clear, and there is no need to distinguish the two in terms of terminology in this embodiment. Therefore, in this specification, when it is called "film", it also includes "sheet", and when it is called "sheet", it also includes "film". In addition, the concept of "film" also specifically includes plastic wrap in the above definition. [Example]

Hereinafter, the present invention will be described in more detail based on embodiments, but the present invention is not limited to the embodiments.

Using the following polyvinyl chloride resins and additives, stretch packaging films having the compositions shown in Table 1 were prepared. In Table 1, the composition (parts by mass) represents the content (parts by mass) of each component relative to 100 parts by mass of the polyvinyl chloride resin, Y1 represents the total content of the plasticizer, Y2 represents the total content of diisononyl adipate and dioctyl adipate (the content of the compound represented by formula (1)), Y1/X1 represents the mass ratio of the total content Y1 of the plasticizer to the content X1 of the blue colorant, Y2/X1 represents the mass ratio of the total content Y2 of diisononyl adipate and dioctyl adipate (the content of the compound represented by formula (1)) to the content X1 of the blue colorant, and Y3/X1 represents the mass ratio of the content Y3 of diisononyl adipate to the content X1 of the blue colorant. In addition, in all the embodiments and comparative examples, the content of the antifogging agent D1 was set to 1.2 parts by mass, the content of the stabilizer E1 was set to 0.15 parts by mass, and the content of the stabilizer E2 was set to 1.1 parts by mass.

Polyvinyl chloride resin ・A1: Polyvinyl chloride resin (manufactured by Taiyo Vinyl Co., Ltd., "TH-1000", average degree of polymerization: 1000)

Plasticizers ・B1: Diisononyl adipate (DINA, manufactured by TAOKA Chemical Industry Co., Ltd., "DINA") ・B2: Dioctyl adipate (DOA, manufactured by Shin Nippon Chemical Co., Ltd., "Sanso Cizer DOA") ・B3: Epoxidized soybean oil (ESBO, manufactured by Sanwa Synthetics Co., Ltd., "Chemicizer SE-100")

Blue colorant ・C1: Blue colorant (manufactured by Dainichi Seika Co., Ltd., "NX-053 Blue")

Anti-mist agent ・D1: (manufactured by Riken Vitamin Co., Ltd., "XO-71")

Stabilizer ・E1: (Made by Kyowa Chemical Industry Co., Ltd., "Alcamaizer 1") ・E2: (Made by ADEKA Co., Ltd., "SC-308E")

More specifically, after each component is put into a high-speed mixer, the material temperature is raised from room temperature to 130°C while being stirred to obtain a resin composition. The obtained resin composition is taken out at a time point when it is cooled to 70°C, and is extruded by a single-axis extruder (L/D=20) with a diameter of 40 mm and equipped with a T-die (width: 350 mm, gap: 0.4 mm) at a temperature of 200°C and wound around a core material to produce a stretch packaging film with a thickness of 15 μm.

<Evaluation of stretch wrap film> The stretchability, peelability, and pull-out properties of each of the obtained stretch wrap films were measured by the following procedure. The results are shown in Table 1.

(Stretchability) Using a stretch wrapping film with a width of 300 mm, a foamed polystyrene pallet (length: 175 mm, width: 120 mm, height: 30 mm) was continuously wrapped five times by a manual wrapping machine (Multi-Wrapper W460B manufactured by ARC Co., Ltd.). The stretchability was evaluated based on the degree of wrinkles (wrinkles on the upper surface of the wrapped pallet) at this time. A: No wrinkles were generated. B: The area of the wrinkles was less than 30% of the film area. C: The area of the wrinkles was more than 30% of the film area. D: Wrinkles were generated on almost the entire surface of the film.

(Peeling property) 40 sheets of stretch wrapping film cut into a size of 250 mm × 150 mm were stacked and left in a constant temperature room at 20°C for 24 hours. The films were attached to a smooth stainless steel plate with a double-sided tape, and the peeling force required to peel off one sheet of film was determined using a tensile testing machine (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.) in a constant temperature room. A: Peeling force less than 150 gf/250 mm B: Peeling force 150 gf/250 mm or more but less than 200 gf/250 mm C: Peeling force 200 gf/250 mm or more but less than 250 gf/250 mm D: Peeling force 250 gf/250 mm or more

(Extraction performance) The film wound around the core material was placed in a box, and the extraction force when the film was extracted from the box was evaluated using a push-pull gauge (manufactured by Aikoh Engineering Co., Ltd.). A: Extraction force less than 500 gf B: Extraction force of 500 gf or more and less than 650 gf C: Extraction force of 650 gf or more and less than 800 gf D: Extraction force of 800 gf or more

[Table 1] Embodiment Comparison Example 1 2 3 4 5 6 7 8 9 10 1 2 Composition (mass) Plasticizer B1 25.00 16.87 19.80 14.50 16.87 20.40 10.87 5.70 10.00 5.70 14.00 5.00 B2 15.00 10.33 14.30 11.30 10.33 13.50 16.33 14.30 10.00 8.62 10.40 10.00 B3 13.9 11 11 7 11 11.20 11 7.7 18.2 13.44 2 8 Blue colorant C1 1.1 0.8 1.1 0.8 1.1 1.3 1.1 0.8 1.1 0.8 1.1 0.8 Y1 53.9 38.2 45.1 32.8 38.2 45.1 38.2 27.7 38.2 27.76 26.40 twenty three Y2 40 27.2 34.1 25.8 27.2 33.9 27.2 20 20 14.32 24.40 15 Y1/X1 49.0 47.8 41.0 41.0 34.7 34.7 34.7 34.6 34.7 34.7 24.0 28.8 Y2/X1 36.4 34.0 31.0 32.3 24.7 26.1 24.7 25.0 18.2 17.9 22.2 18.8 Y3/X1 22.7 21.1 18.0 18.1 15.3 15.7 9.9 7.1 9.1 7.1 12.7 6.3 Stretchability A A A B A A A B A B D D Separability B B B A A A B A B A C D Extractable B B A A A A A A B B C D

without

without

Claims (3)

A stretch wrapping film comprises a polyvinyl chloride resin, a plasticizer, and a blue coloring agent, wherein the plasticizer comprises a compound represented by the following formula (1):

In formula (1), ^R1 and ^R2 each independently represent an alkyl group, the mass ratio of the content of the plasticizer to the content of the blue colorant is 30 or more and 45 or less, the mass ratio of the content of the compound represented by formula (1) to the content of the blue colorant is 20 or more and 33 or less, and the mass ratio of the content of the compound in which ^R1 and ^R2 in formula (1) are alkyl groups having 9 carbon atoms to the content of the blue colorant is 6 or more and 20 or less. The stretch wrapping film as described in claim 1, wherein the plasticizer further comprises epoxidized soybean oil. The stretch wrap film according to claim 1 or claim 2, wherein the mass ratio of the content of the compound in which ^R1 and ^R2 in the formula (1) are alkyl groups having 9 carbon atoms to the content of the blue coloring agent is 15 or more and 20 or less.