JP2004276320A - Laminated film for thermal fusion with natural materials - Google Patents

Abstract

An object of the present invention is to provide a heat-sealing laminated film used for heat-sealing with a natural material, which does not impair the environmental characteristics of the natural material and has excellent continuous productivity.
A heat-sealing laminated film comprising an outermost layer and an innermost layer containing an aliphatic polyester as a main component, wherein the melting point Tm1 of the aliphatic polyester constituting the outermost layer measured according to JIS K-7121. Tm1−Tm2 (Tg2) ≧ 25 ° C. is satisfied between the melting point Tm2 (or glass transition point Tg2) of the aliphatic polyester constituting the innermost layer to be the heat-sealing surface and measured according to JIS K-7121. I did it.
[Selection diagram] None

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat-sealing laminated film used for bonding to a natural material in order to supplement the strength and water resistance of the natural material while maintaining the environmental characteristics of the natural material.
[0002]
[Prior art]
In the packaging field, plastics such as polystyrene, polypropylene, polyethylene, polyvinyl chloride, and polyethylene terephthalate are used in large quantities.Natural materials have been attracting attention as plastic disposal problems have recently been highlighted. ing. For example, natural materials such as wood pulp and vegetable waste are mainly made of plants, so whether they are landfilled or incinerated, the carbon source ultimately passes through carbon dioxide and is again planted by photosynthesis. Is reduced to Unlike one-way plastics derived from petroleum resources, it is a material that is circulated in the global environment and has excellent environmental suitability from the viewpoints of effective use of resources, disposal of waste, and prevention of increase in atmospheric carbon dioxide. It is evaluated as a material.
[0003]
Since natural materials of this kind are inferior in strength, water resistance, suitability for mechanical packaging and the like as compared with plastics and the like, it is necessary to compensate for these drawbacks when finishing products.
Conventionally, there have been examples in which a paper cup is combined with a drawn polystyrene cover material, or polyethylene or polypropylene is extruded and laminated on a raw paper of paper in order to impart water resistance to a paper tray.
[0004]
However, even if the product is made mainly of natural materials, if non-biodegradable plastic is compounded even partially, it cannot be said that the product as a whole is environmentally compatible. It has been proposed to use a biodegradable plastic as a plastic to be composited with a material.
For example, a biodegradable composite material obtained by coating a surface of a substrate containing vegetable fibers with polylactic acid or a derivative thereof (for example, see Patent Document 1), or a copolymer of polylactic acid or lactic acid and oxycarboxylic acid is used. A decomposable laminated paper obtained by laminating a thermoplastic decomposable polymer as a main component on paper (for example, see Patent Document 2), or a thermoplastic decomposable resin containing polylactic acid or a copolymer of lactic acid and oxycarboxylic acid as a main component. A degradable laminate composition obtained by laminating a polymer on a regenerated cellulose film (for example, see Patent Document 3), a laminate of paper and a biodegradable oriented polylactic acid film (for example, see Patent Document 4), etc. Is disclosed.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 4-334448 [Patent Document 2]
JP-A-4-336246 [Patent Document 3]
JP-A-5-38784 [Patent Document 4]
JP-A-8-252895 [0006]
[Problems to be solved by the invention]
Normally, when a natural material and a biodegradable film are combined, a synthetic adhesive is used as the adhesive, but strictly speaking, even if a small amount of the synthetic adhesive is used, the environmental characteristics of the natural material may be impaired. Become.
On the other hand, Patent Literature 2 and the like propose that gelatin, which is a natural product, is used as an adhesive. In this case, it is necessary to keep pressing at a predetermined pressure overnight, for example. There was a problem that continuous productivity was poor and it was difficult to use it industrially.
[0007]
Therefore, an object of the present invention is to focus on a method of thermally bonding a natural material and a biodegradable film to each other without using an adhesive to form a composite, and without impairing the environmental characteristics of the natural material, and further improving continuous productivity. An object of the present invention is to provide an excellent heat-sealing laminated film.
[0008]
By the way, as a method for continuously heat-sealing a plastic film to a natural material, generally the following two methods are mainly considered.
One is a method in which a natural material sheet or plate and a heat-sealing film are sandwiched between two rotating rolls and heat-sealed. In general, the heat-sealing film in this case is that the film can be heat-sealed at as low a temperature as possible, that the film is not adhered to the roll, and that the film does not shrink during heat-sealing. Desired.
The other is a method in which a heat-sealing film is laminated on a surface of a pre-formed natural material molded body and heat-sealed in a mold for vacuum forming or pressure forming. In this case, the heat-sealing film is generally required to be heat-seamable at as low a temperature as possible, to be difficult to draw down when heating the film, and to have low shrinkage during heat-sealing.
[0009]
[Means for Solving the Problems]
The present invention comprises an outermost layer and an innermost layer containing an aliphatic (including aromatic aliphatic) polyester as a main component, that is, an outermost layer containing an aliphatic (including aromatic aliphatic) polyester as a main component. And an innermost layer containing aliphatic polyester (including aromatic aliphatic) as a main component,
The melting point Tm1 measured by JIS K-7121 of the aliphatic polyester constituting the outermost layer and the melting point Tm2 or melting point measured by JIS K-7121 of the aliphatic polyester constituting the innermost layer to be the heat-sealing surface are recognized. If not, the following relational expression (1) is applied to the glass transition point Tg2.
Tm1−Tm2 or Tg2 ≧ 25 ° C. (1)
The present invention proposes a laminated film for heat-sealing with a natural material, characterized in that:
The case where the melting point is not recognized includes the case where the melting point is not recognized at all and the case where the melting point is not clearly recognized, for example, when the resin is amorphous and the melting point is not recognized.
[0010]
When heat-sealing via a heat-sealing film, the heat-sealing film must be heated to its softening point or higher.For example, when a single-layer heat-sealing film made of aliphatic polyester is used, a heat roll This causes problems such as the film sticking to the film, the drawdown being large, the film not being formed uniformly, and the softened film coming into contact with a mold or the like. On the other hand, according to the heat-sealing laminated film having the configuration of the present invention, these problems can be eliminated and continuous production can be suitably performed. Therefore, if the innermost layer surface of the heat-sealing laminated film of the present invention is heat-sealed to a natural material as a heat-sealing surface to form a molded body, it can be manufactured more efficiently at lower cost.
Further, since the heat-sealing laminated film of the present invention can be composed of only a biodegradable or biodegradable material, if a natural material molded article is produced by heat-sealing to a natural material, natural A molded article supplementing the strength and water resistance of a natural material while maintaining the environmental properties of the material can be obtained.
[0011]
In the present invention, `` having an aliphatic polyester as a main component '' includes a meaning that other components may be contained as long as the function of the aliphatic polyester is not impaired. Generally, the content is about 50% or more, preferably 80%.
The same applies to the case where a component other than the aliphatic polyester is used as a main component.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0013]
The heat-sealing laminated film of the present invention (also simply referred to as “laminated film”) is a laminated film used for heat-sealing to a natural material, and comprises an outermost layer containing an aliphatic polyester as a main component, and the outermost layer. And an innermost layer containing aliphatic polyester having a melting point or a glass transition point having a predetermined relationship with the melting point of the aliphatic polyester of the outer layer as a main component.
[0014]
The `` aliphatic polyester '' which is a main component of the outermost layer and the innermost layer includes an aromatic aliphatic aliphatic polyester, for example, a polyhydroxycarboxylic acid containing a polylactic acid-based polymer, an aliphatic diol and an aliphatic dicarboxylic acid. And aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones, synthetic aliphatic polyesters, aliphatic polyesters biosynthesized in cells, and the like. Each aliphatic polyester will be described in detail below.
Note that, of the outermost layer and the innermost layer, at least the outermost layer, that is, the layer on the side opposite to the innermost layer serving as the heat fusion surface is preferably formed mainly of a polylactic acid-based polymer. The polylactic acid-based polymer is particularly excellent in transparency among aliphatic polyesters having biodegradability, and can make the appearance of the product after fusion more beautiful.
[0015]
Examples of the above-mentioned "polylactic acid-based polymer" include poly (L-lactic acid) whose main structural unit is L-lactic acid, poly (D-lactic acid) whose main structural unit is D-lactic acid, and main structural units. Is poly (DL-lactic acid), which is L-lactic acid and D-lactic acid, or a mixture containing these as a main component.
The above "main structural unit" means that other monomer units may be contained as long as the effects of the present invention are not impaired. For example, it may be a copolymer with “another hydroxycarboxylic acid unit”, and if necessary, as a small amount of a copolymer component, a non-aliphatic dicarboxylic acid such as terephthalic acid and / or bisphenol A And a non-aliphatic diol such as an ethylene oxide adduct of the present invention.
The structure of the polylactic acid, that is, the ratio of D-lactic acid to L-lactic acid can be appropriately selected in consideration of a desired melting point. Generally, a polylactic acid-based polymer consisting of only D-lactic acid or only L-lactic acid becomes a crystalline resin and tends to have a high melting point. It is known that the crystallinity of DL-lactic acid decreases as the ratio of the optical isomer increases.
It is also possible to blend two or more kinds of polylactic acids having different composition ratios of D-lactic acid and L-lactic acid.
Examples of the “other hydroxycarboxylic acid unit” copolymerized with polylactic acid include optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), glycolic acid , 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid and the like Lactones such as bifunctional aliphatic hydroxycarboxylic acid, caprolactone, butyrolactone, valerolactone, and the like can be mentioned.
The weight average molecular weight of the polylactic acid-based polymer is preferably 60,000 to 1,000,000, and more preferably 80,000 to 400,000. If it is about 60,000 or more, necessary practical physical properties can be obtained, and if it is about 400,000 or less, the melt viscosity is not too high and the moldability is excellent.
[0016]
For the purpose of adjusting the toughness, flexibility, biodegradation rate and the like of the polylactic acid-based polymer, it is also possible to blend “other biodegradable aliphatic polyester” with the polylactic acid-based polymer.
Examples of the “other biodegradable aliphatic polyester” include polyhydroxycarboxylic acids excluding polylactic acid-based polymers, aliphatic polyesters obtained by condensing aliphatic diols and aliphatic dicarboxylic acids, and cyclic lactones. Examples thereof include aliphatic polyesters obtained by ring polymerization, synthetic aliphatic polyesters, and aliphatic polyesters biosynthesized in cells. Details will be described later.
At this time, the amount to be blended may be appropriately adjusted according to desired physical properties such as transparency, flexibility, and adhesiveness. For example, if transparency is emphasized for the purpose of ensuring the transparency of the container, the lactic acid-based polymer / biodegradable aliphatic polyester is preferably in the range of 50/50 to 97/3.
Further, a small amount of a chain extender, for example, a diisocyanate compound, an epoxy compound, an acid anhydride or the like can be used for the purpose of increasing the molecular weight.
Furthermore, behenic acid, stearic acid, pentathritol monoester, pentaerythritol diester, pentaerythritol tetrastearate, pentaerythritol-adipate-stearate complex ester, dipentaerythritol-adipate-stearate complex ester , Lubricants such as dipentaerythritol hexastearate, plasticizers such as dioctyl phthalate, various surfactants such as acetylene glycol, acetylene alcohol, glycerin aliphatic esters and polyglycerin aliphatic esters, dyes, pigments and other additives Alternatively, a polymer may be added to the above-mentioned polylactic acid-based polymer.
[0017]
Examples of the above-mentioned "polyhydroxycarboxylic acid" other than the polylactic acid-based polymer include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, and 2-hydroxybutyric acid. Examples thereof include homopolymers and copolymers of hydroxycarboxylic acids such as -3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid.
[0018]
As the above-mentioned “aliphatic polyester obtained by condensing aliphatic diol and aliphatic dicarboxylic acid”, one or more kinds of aliphatic diols and aliphatic dicarboxylic acids are respectively selected from the aliphatic diols and aliphatic dicarboxylic acids described below. Alternatively, if necessary, the desired polymer (polymer) can be obtained by jumping up with an isocyanate compound or the like.
Typical examples of the “aliphatic diol” at this time include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like. Representative examples thereof include acids, adipic acid, suberic acid, sebacic acid, dodecane diacid, and the like.
In addition, an aromatic aliphatic polyester obtained by copolymerizing an appropriate amount of an aromatic dicarboxylic acid is also included in these categories. In order to express biodegradability in the aromatic aliphatic polyester, it is necessary that an aliphatic chain is present between aromatics, and in this case, as an aromatic dicarboxylic acid component, for example, isophthalic acid, Examples thereof include terephthalic acid and 2,6-naphthalenedicarboxylic acid.
[0019]
As the above-mentioned “aliphatic polyester obtained by ring-opening polymerization of a cyclic lactone”, as a cyclic monomer, one or more kinds of ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like are polymerized. Can be manufactured.
[0020]
Examples of the above-mentioned "synthetic aliphatic polyester" include cyclic acid anhydrides and oxiranes, for example, copolymers of succinic anhydride with ethylene oxide, propion oxide and the like.
[0021]
Examples of the above-mentioned "aliphatic polyester biosynthesized in cells" include aliphatic polyester biosynthesized by acetyl coenzyme A (acetyl CoA) in cells such as alkaligenes eutrophus. This aliphatic polyester is mainly poly-β-hydroxybutyric acid (poly 3HB), but in order to improve practical properties as a plastic, a valeric acid unit (HV) is copolymerized to obtain poly (3HB-CO-3HV). It is industrially advantageous to use the copolymer of (1). Generally, the HV copolymerization ratio is 0 to 40%. Further, a long-chain hydroxyalkanoate may be copolymerized.
[0022]
The aliphatic polyester used in the present invention is an aliphatic polyester as a polymer having a weight average molecular weight of 10,000 to 500,000, preferably a molecular weight of 50,000 to 300,000, and more preferably 100,000 to 300,000. A distinction is made from the low molecular weight aliphatic polyesters used. The difference between the two appears in the presence or absence of a decrease in the glass transition temperature (Tg) of the lactic acid-based resin to be blended.
[0023]
In the configuration of the laminated film of the present invention, from the aliphatic polyesters described above, it is possible to select an aliphatic polyester that is a main component of the outermost layer and an aliphatic polyester that is a main component of the innermost layer. when, the melting point Tm1 measured at JIS K-7121 of the aliphatic polyester constituting the outermost layer, the melting point _Tm 2 measured at JIS K-7121 of the aliphatic polyester which constitutes the innermost layer of the heat Chakumen ( If no melting point is found, it is necessary to select a combination so that the following relational expression (1) is satisfied between the melting point and the glass transition point Tg2).
Tm1−Tm2 or Tg2 ≧ 25 ° C. (1)
[0024]
When there is a difference of 25 ° C. or more, more preferably 30 ° C. or more between Tm1 and Tm2 or Tg2, when the laminated film of the present invention is sandwiched between two rolls together with a natural material and thermally fused, the laminated film is used. Even if is heated to the melting point Tm2 or the glass transition point Tg2 or more, the outermost layer does not melt unless it is heated to the Tm1 or more, so that the laminated film does not stick to or take off from the roll, and can be smoothly and continuously produced. be able to. Also, in the case of laminating a laminated film on a surface of a preformed molded material of a natural material in a mold of vacuum forming or pressure forming, and heat-sealing, the outermost layer does not melt unless heated to Tm1 or more. In addition, it does not draw down when the film is heated and does not come into contact with the molded body of the natural material, so that the natural material and the laminated film can be continuously and smoothly fused to each other.
As long as the relational expression (1) is satisfied, the same kind of aliphatic polyester can be combined as a main component of the outermost layer and the innermost layer. For example, both the outermost layer and the innermost layer can contain a polylactic acid-based polymer as a main component.
Further, the glass transition point Tg can be reduced by mixing an appropriate low-molecular compound (plasticizer).
[0025]
The laminated film of the present invention may be a laminated film composed of two layers of an outermost layer and an innermost layer, or a laminated film composed of three or more layers of an outermost layer, an intermediate layer and an innermost layer. At this time, the intermediate layer sandwiched between the outermost layer and the innermost layer can be arbitrarily configured. However, in consideration of maintaining the environmental characteristics of the natural material, the intermediate layer can be formed from only a biodegradable material or a biodegradable material (including a natural material). It is preferred to form a layer. The melting point or glass transition point of the intermediate layer is not particularly limited.
[0026]
Next, a preferred example of the laminated film of the present invention will be described. However, it is not limited to this manufacturing method.
First, the polymer or blend composition constituting each layer is extruded, calendered, processed into a planar or cylindrical shape by a general melt molding method such as a press method to obtain a sheet-like material, if necessary. In order to improve mechanical properties such as strength, the sheet-like material is uniaxially or biaxially stretched by a roll method, a tenter method, a tubular method, an inflation method and the like, and further, if necessary, the heat resistance of the stretched film. In order to improve (thermal dimensional stability), heat treatment is performed after stretching.
Next, the above-mentioned sheet-like material is laminated to form a laminated film. At this time, as a laminating method, a co-extrusion method using a feed block method or a multi-manifold die using two or more extruders, or a separate And a laminating method such as extruding and laminating a film formed with a film formed in advance with an adhesive. Among them, a co-extrusion method is generally used from the viewpoint of productivity and the like.
The thickness of the laminated film is 5 μm to 300 μm, and more preferably 10 μm to 100 μm.
[0027]
(Natural material molding)
The heat-sealing laminated film of the present invention is heated to a temperature not lower than Tm2 or Tg2 and lower than Tm1, heat-fused to the natural material with the innermost layer surface as a heat-sealing surface, and appropriately molded to form the natural film of the present invention. A material molded body can be manufactured.
[0028]
At this time, the heating temperature of the heat-sealing laminated film is preferably 5 ° C. or more lower than Tm1 and 5 ° C. or more higher than Tm2 or Tg, and more preferably 10 ° C. or more lower than Tm1. The temperature range is at least 10 ° C. higher than Tg, particularly preferably at least 15 ° C. lower than Tm1 and at least 15 ° C. higher than Tm2 or Tg.
[0029]
As the "natural material", at least one material selected from the group consisting of the following 1) to 5) can be listed as the main material, and the material has biodegradability similar to these materials. Materials can also be used.
1) Wood pulp 2) Recycled wood pulp obtained from recovered waste paper 3) Non-wood vegetable pulp obtained from kenaf, reed, hemp, bamboo, etc. 4) Rice husk, rice straw, straw, sawdust, beer waste, and beer 5) Wood sheets and wood chips
The natural material contains inorganic fillers such as calcium carbonate, talc, and mica, and additives such as starch, cellulose, polysaccharides such as amylopectin, wax, pine tar, and resin as various physical property modifiers. Is also good.
[0031]
Embodiment 1
Polylactic acid Natureworks 4031D made by Cargill Dow for the outermost film
(D%: 1.5%, Tm: 165 ° C.), after being dehumidified and dried, fed to a φ65 mm single screw extruder, while being used for the innermost layer film, polylactic acid Natureworks 4060D made by Kirky Dow (D%: 12%, Tg : 58 ° C.) after dehumidifying and drying, fed to a φ4 mm single screw extruder, extruded into a film form from a 1000-width multi-manifold type T die set at 200 ° C., and then contacted with a 40 ° C. cast roll, A laminated film having a thickness of 50 μ was obtained. The thickness ratio between the outermost layer and the innermost layer was 4: 1 (40 μ / 10 μ).
[0032]
Using the obtained laminated film, heat fusion to kraft paper was performed by a test laminator equipped with a heating roll heated to 120 ° C.
As a result, a good heat-sealed laminate was obtained without removing the film from the roll.
[0033]
Embodiment 2
Using the laminated film obtained in Example 1, the laminated film previously heated to 120 ° C. in a pre-formed reed tray was placed on a reed tray and placed on the reed tray from below. By suctioning in a vacuum, the thermoforming of the film and the heat fusion to the reed tray were simultaneously performed.
As a result, a good heat-sealed reed tray was obtained without drawdown trouble.
[0034]
Embodiment 3
Polylactic acid Natureworks4031D made by Kirkirdow for the outermost film
(D%: 1.5%, Tm: 165 ° C.), and then supplied to a φ65 mm single screw extruder, while an aliphatic polyester bionore # 3003 (Tm) made by Showa Polymer for the innermost layer film. : 95 ° C.) after dehumidifying and drying, fed to a φ4 mm single screw extruder, extruded into a film form from a 1000-width multi-manifold type T die set at 200 ° C., and then contacted with a 40 ° C. cast roll, A laminated film having a thickness of 50 μ was obtained. The thickness ratio between the outermost layer and the innermost layer was 4: 1 (40 μ / 10 μ).
[0035]
Using the obtained laminated film, heat fusion to kraft paper was performed by a test laminator equipped with a heating roll heated to 120 ° C.
As a result, a good heat-sealed laminate was obtained without removing the film from the roll.
[0036]
[Comparative Example 1]
For the outermost film, polylactic acid Natureworks4031D made by Cargill Dow
(D%: 1.5%, Tm: 165 ° C.), dehumidified and dried, fed to a φ65 mm single screw extruder, extruded into a film form from a 1000 width T-die set at 200 ° C., and then extruded at 40 ° C. The film was brought into contact with a cast roll to obtain a single-layer film having a thickness of 50 µm.
[0037]
Using the obtained single-layer film, heat fusion to kraft paper was performed with a test laminator equipped with a heating roll heated to 150 ° C. Could not be thermally fused.
[0038]
[Comparative Example 2]
Using the single-layer film obtained in Comparative Example 1, the above-mentioned single-layer film preheated to 150 ° C. was placed on a pre-formed reed tray and placed on a reed tray. Thermoforming of the film and heat-sealing to the reed tray were performed simultaneously by suctioning from the side with a vacuum, but good heat-sealed reed trays were obtained due to partial contact with the reed tray by drawdown. Could not get.
[0039]
[Comparative Example 3]
For the outermost film, polylactic acid Natureworks4031D made by Cargill Dow
(D%: 1.5%, Tm: 165 ° C), and then supplied to a φ65 mm single screw extruder, while Cargill Dow polylactic acid Natureworks 4050D (D%: 6%, Tm: 145 ° C.), dehumidified and dried, fed to a φ40 mm single screw extruder, extruded into a film form from a multi-manifold type T die of 1000 mm width set at 200 ° C., and then contacted with a 40 ° C. cast roll And a two-layer laminated film having a thickness of 50 μm. The thickness ratio between the outermost layer and the innermost layer was 4: 1 (40 μ / 10 μ).
[0040]
Using the obtained laminated film, heat fusion to kraft paper was performed with a test laminator equipped with a heating roll heated to 150 ° C. Thermal fusion could not be performed.

Claims (4)

With an outermost layer and an innermost layer containing an aliphatic polyester as a main component,
The melting point Tm1 measured by JIS K-7121 of the aliphatic polyester constituting the outermost layer and the melting point Tm2 or melting point measured by JIS K-7121 of the aliphatic polyester constituting the innermost layer to be the heat-sealing surface are recognized. If not, the following relational expression (1) is applied to the glass transition point Tg2.
Tm1−Tm2 or Tg2 ≧ 25 ° C. (1)
The laminated film for heat fusion with a natural material, characterized in that: 2. The laminated film for thermal fusion with a natural material according to claim 1, wherein the aliphatic polyester constituting the outermost layer comprises a polylactic acid-based polymer. A natural material molded article having a configuration obtained by heat-sealing the heat-sealing laminated film according to claim 1 or 2 to a natural material. A method for producing a natural material molded product, comprising: forming a heat-sealing surface of the innermost layer of the heat-sealing laminated film according to claim 1 or 2 as a heat-sealing surface;