JPH0741702B2 - Food container paper laminated material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a food container paper laminate material, and more particularly to a milk carton, a juice carton, a frozen dessert container which is inexpensive, has no curl and has high rigidity. , A paper laminated material suitable for food containers such as frozen food containers, cups, trays and lunch boxes.

[Conventional technology and problems]

Conventionally, as a material for food containers of this type, 300 to 400 g / m ²
The cardboard used in the above process is used as a base paperboard, and low-density polyethylene is laminated on both sides of the cardboard, and aluminum foil is further laminated.

However, as mentioned above, since we rely exclusively on imports for cardboard, as mentioned above, it is difficult to obtain stable stable supplies because it is easily affected by the political and economic conditions of the importing country. Is also a big issue. As a method to solve this problem, it is possible to make 300-400 g / m ² thick paper in Japan, but there are problems such as new capital investment and the establishment of technology accompanying it.

[Means for solving problems]

In view of such circumstances, the present inventors provide a stable, inexpensive curl-free and highly rigid food container / paper laminate material in Japan without requiring new capital investment or establishment of advanced technology. As a result of intensive research, the present invention has been completed.

That is, the present invention relates to a food container paper laminated material characterized by using a thick paper obtained by laminating a plurality of thin papers through a perforated extrusion laminated resin layer.

The thin paper used in the present invention is not particularly limited, but 80 to 200 g / m ² is suitable. If it is too thin, the number of sheets to be bonded increases and the rigidity is improved but the productivity is lowered, which is not preferable. The number of sheets to be stuck together is preferably 2 to 4. When 3 to 4 sheets are stuck together, the cost can be reduced by using the waste paper as the central paper.

For bonding thin paper, use of adhesives and pressure sensitive adhesives, hot melt lamination, dry lamination, wet lamination, extrusion lamination, etc. can be used, but when using adhesives and pressure sensitive adhesives, use of organic solvents Are required, and in the case of wet lamination, there are problems such as impaired water resistance, which are not preferable. Therefore, the perforation extrusion laminating method is preferable. According to the perforation extrusion laminating method, curling does not occur as described later,
Moreover, since the thickness increases due to the perforation as compared with the papermaking paper having the same basis weight as the cardboard to be laminated, the effect of improving the rigidity can be expected. Perforation extruded laminate layer weight is 20-40g / m ²
Is preferred.

The base resin used for punch-through extrusion lamination is not particularly limited as long as it is a thermoplastic resin, but the adhesiveness of polyethylene, polypropylene, polystyrene, polyester, polycarbonate, polyamide, polyvinyl alcohol and copolymers containing these as the main components, etc. Resins are preferable, and these are used alone or in combination of two or more. A moisture-permeable hydrophilic resin is particularly suitable.

Low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), olefin-acrylic acid ester copolymer for extruded laminating resin to improve adhesiveness with paper , Olefin-
Acrylic acid copolymer, olefin-maleic anhydride copolymer, olefin-itaconic acid copolymer, olefin-
It is also possible to mix an adhesion-enhancing resin such as an acrylate copolymer. The compounding amount of the adhesion enhancing resin is preferably 1 to 50% by weight.

In the present invention, one or more kinds of a foaming agent, a tackifier (tackifier) filler and the like are blended in the extruded laminated resin, and as described later, foaming, gas generation due to thermal decomposition, or voids. By forming a perforated laminate by the formation of, to give air permeability and moisture permeability to the cardboard of the material of the present invention, contribute to the reconstitution of hydrogen bonds in the molecules that compose the paper on both sides, and relax the strain, as a result. Curling is prevented and the shape is stabilized.

In addition, in the present invention, a compatibilizing agent may be added to the extrusion laminated resin in addition to the above-mentioned compounding agent.

The foaming agent used in the present invention is a substance having a boiling point or a decomposition temperature lower than the heat distortion temperature or melt extrusion temperature of the extrusion laminate resin, and an aliphatic hydrocarbon as an organic foaming agent,
There are halogenated aliphatic hydrocarbons and others. Examples of the aliphatic hydrocarbons are saturated aliphatic hydrocarbons such as propane, butane, pentane and hexane, and unsaturated aliphatic hydrocarbons such as propylene and butene. Examples of halogenated aliphatic hydrocarbons are methyl chloride, methylene chloride, dichlorodifluoromethane and the like. Other organic foaming agents include azodicarbonamide (ADCA), azobisisobutyronitrile (AIBN), N, N'-dinitrosopentamethylenetetramine (DPT), p-toluenesulfonyl hydrazide (TSH), p, p A general synthetic resin foaming agent such as'-oxybis (benzenesulfonyl hydrazide) (OBSH) is used. These can be used alone or in combination of two or more.

In addition to the above organic foaming agents, crystal water-containing inorganic compounds are also used as foaming agents, which are generally called crystal waters (coordinating to salt ions as water molecules, lattice water, structural water). It refers to an inorganic compound containing fluorite water, and particularly preferable ones are gypsum, magnesium hydroxide, aluminum hydroxide and the like. These inorganic foaming agents are of one type or two types.
Used as a mixture of more than one species.

The mixing ratio of the foaming agent varies depending on the foaming gas generation amount of the foaming agent, the extrusion temperature, the melt viscosity of the resin, the laminate weight, etc., but is usually 0.05 with respect to 100% by weight of the extruded laminated resin.
-50% by weight, preferably 0.1-5.0% by weight.

The tackifier used in the present invention has a plasticizing effect of the extruded laminated resin, and is thermally decomposed by heat during laminating to generate gas, thereby forming fine voids on the film layer and its surface.

The tackifier used in the present invention includes terpene type, rosin type, petroleum resin type, maleic acid resin type, phenol resin type and the like, and these are used alone or as a mixture of two or more kinds. The content of the resin composition is preferably in the range of 2 to 20% by weight in the resin composition. If it is less than 2% by weight, the above effect is not sufficiently exhibited, and if it exceeds 20% by weight, the laminating property is deteriorated.

The filler in the present invention includes not only an inorganic substance but also an organic substance, and its shape such as a particulate form or a fibrous form is favorably applied. The first purpose of incorporating the inorganic filler is to promote void formation by functioning as a nucleating agent. The second purpose is to use the heat during lamination to gasify the adhering water and crystallization water of the inorganic filler, and to use the thermal decomposition gas of the inorganic filler itself to further increase the void formation amount. This is to form open cells and give air permeability. This prevents curling and improves shape stability.

Examples of the inorganic filler used in the present invention include calcium carbonate, silica, mica, talc, clay, zeolite, alumina, titanium oxide, tin oxide, glass powder, barium sulfate, bentonite, diatomaceous earth, gypsum and sodium hydrogen carbonate. On the other hand, examples of the organic filler include urea resin, phenol resin, thermosetting polyester resin, silicone resin, polystyrene resin, and methyl methacrylate resin. These may be used alone or in combination of two or more depending on the purpose of use. Filler content is 0.5-40% by weight
Is preferable, and if it is less than 0.5% by weight, the void formation promoting effect is small, and if it exceeds 40% by weight, the laminating processability is deteriorated. The blending amount is appropriately determined according to the laminating temperature, the amount of generated gas, and the like.

The compatibilizing agent used in the present invention acts on the extruded laminated resin, the tackifier, the filler, and the gas forming the voids, which form the resin composition, to make the voids formed uniform and fine. It is intended. Desirable as the compatibilizer is a surfactant, for example, a high molecular weight propylene oxide or a functional group-containing olefin resin (maleic anhydride copolymer, acrylic acid copolymer, itaconic acid copolymer, etc.), Polymer compounds such as ethylene vinyl alcohol copolymer and α-olefin adduct of polymethyl hydrogen siloxane can be used. The selection and blending amount of the compatibilizer are determined by the blending ratio of each component constituting the resin composition, the HLB value, and the like. Depending on the type of compatibilizer, it has a void forming ability by thermal decomposition. A suitable blending ratio is usually in the range of 0.1 to 15% by weight.

A laminate layer is provided on one side or both sides of the cardboard obtained as described above to obtain a food container paper laminated material.

This laminating layer is formed by a known method such as an extrusion laminating method, a hot melt laminating method, a dry laminating method, a wet laminating method, a laminating method with an adhesive or a pressure sensitive adhesive, and one or more layers are formed on one side or both sides. It is provided.

As the laminate layer, the above-mentioned thermoplastic resin (adhesive resin), those in which an adhesion-enhancing resin, tackifier, and a filler are appropriately blended, as well as metal foil, metal vapor deposition film and the like are used.

Further, in order to enhance the adhesiveness between the laminate layers, a known method such as corona discharge treatment, flame treatment or ozone treatment, or providing an anchor coat layer is used. Further, corona discharge treatment or the like for improving print recording property on the surface of the laminate layer is generally used.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to these.

Example 1 67% by weight of polypropylene "LA-221" (manufactured by Mitsui Petrochemical Industry Co., Ltd.), 25% by weight of calcium carbonate "Whiten SB (red)" (manufactured by Shiraishi Calcium Co., Ltd.) as a filler, and a foaming agent. Hydroxide "Hijirite H-32" (manufactured by Showa Light Metal Co., Ltd.) as an additive, and a modified polyolefin resin "Admar QE-05" as a compatibilizer
0 "(Mitsui Petrochemical Co., Ltd.) 5% by weight and modified terpene resin" Clearon P- as tackifier "
125 "(Yasuhara Chemical Co., Ltd.) 2% by weight resin composition with T-die extruder (screw diameter 40 mm, L / D
= 22) and extruded under the conditions of T-die outlet resin temperature of 285 ° C. and screw rotation speed of 40 rpm. As a base material, high-quality paper (basis weight 157 g / m ² ) was fed from the first feeding machine, and the surface in contact with the resin composition was previously subjected to corona discharge treatment (32 W / m ² / mi).
n) was applied.

On the other hand, the same high-quality paper as the second base material (weight 15
7 g / m ² ) is fed from the second feeding machine, and the surface in contact with the resin is subjected to corona discharge treatment (32 W / m ² / min) in advance so that the resin composition is sandwiched in between (generally called a sandwich laminate). Then, they were pressure-bonded with a metal roll (surface temperature 20 ° C.) and a press roll, and sandwich lamination processing was performed with a resin weight of 33 g / m ² . As a result, a cardboard having a perforated polysandwich laminate layer with a basis weight of 347 g / m ² having the following three-layer structure was obtained.

The obtained cardboard was excellent in stabilizing the shape by preventing curling because hydrogen bonds in both sides of the paper were reconstituted by the water vapor permeability of the resin composition layer having open cells to take strain. .

Further, since the resin composition layer contains bubbles, the thickness increases,
In this example, the thickness was 40 μm, and it was confirmed that the rigidity was improved as compared with the laminated cardboard of Comparative Example 1 to be described later in which a resin layer of polypropylene alone containing no additive was used.

Then, using this cardboard as a base material and using the T-die extruder described above, low-density polyethylene "Mirason 16P" (manufactured by Mitsui Petrochemical Industry Co., Ltd.) was previously corona-discharge treated (30
W / m ² / min) and then extrusion laminated to a thickness of 28 μm. Then, the same back surface of the substrate was previously subjected to the same corona discharge treatment, and then "Mirason 16P" was extruded and laminated in a thickness of 16 µm to obtain a frozen dumpling container paper laminated material.

Comparative Example 1 A thick paper having a basis weight of 347 g / m ² having the following three-layer structure was obtained in the same manner as in Example 1 except that polypropylene “LA-221” alone was used instead of the resin composition in Example 1. It was The resin layer of this cardboard had a thickness of 36 μm.

The obtained cardboard was curled as compared with the cardboard obtained in Example 1 and was insufficient in rigidity.

Using this cardboard as a base material, "Mirason 16SP" was extrusion laminated on both sides in the same manner as in Example 1 to obtain a frozen dumpling container paper laminated material. The shape stability of this laminated material is shown in Example 1.
It was inferior to that of the laminated material.

Example 2 Low-density polyethylene "Mirason 206P" (manufactured by Mitsui Petrochemical Industry Co., Ltd.) 85% by weight, zeolite "LZ-Y52" (manufactured by Union Showa Co., Ltd.) 5% by weight and tackifier "Clearon P". -125 "10% by weight of a resin composition is used, and fine paper (basis weight 104.8 g / m ² )
The two sheets were laminated by the extrusion sandwich laminating method in the same manner as in Example 1 at a basis weight of 25 g / m ² . However, the T-die outlet resin temperature was 300 ° C and the metal roll surface temperature was 50 ° C. As a result, a cardboard having a perforated resin layer and having a basis weight of 235 g / m ² ) having the following three-layer structure was obtained. The thickness of the perforated resin composition for this cardboard was 30 μm.

Since the obtained cardboard has the perforated resin layer as the intermediate layer, it has water vapor permeability, and therefore relaxes strain and prevents curling. Further, the rigidity was excellent as compared with a laminated cardboard having a polyethylene resin intermediate layer containing no additive having a similar basis weight (Comparative Example 2 described later).

Next, using this cardboard as a base material and using the above-mentioned T-die extruder, low-density polyethylene "Mirason 16SP" was extrusion laminated on one side with a thickness of 20 μm in the same manner as in Example 1,
A cup paper laminate material was obtained.

This laminated material is excellent in rigidity of the heat-sealing portion of the top curl portion and the body bonding portion after molding into a cup,
Further, when a cold beverage was poured, the rigidity was not impaired even if dew condensation occurred on the outer surface of the cup. That is, a paper laminated material having good shape stability was obtained.

Comparative Example 2 A cardboard having a basis weight of 235 g / m ^{2 with} the following three-layer structure was prepared in the same manner as in Example 2 except that the low density polyethylene “Milason 206P” was used alone instead of the resin composition in Example 2. Got The thickness of the resin layer of this cardboard was 27 μm.

The obtained cardboard was more likely to curl and inferior in rigidity than the cardboard obtained in Example 2.

Then, using this cardboard as a base material, "Mirason 16SP" was single-sided extrusion laminated to a thickness of 20 μm in the same manner as in Example 2 to obtain a cup paper laminate material. The present laminated material had a loss of rigidity when no moisture was formed on the outer surface of the cup when it was formed into a cup and a cold beverage was poured.

[Action / effect]

As described above, according to the present invention, it is possible to provide a curl-free food container / paper laminate material inexpensively and easily with conventional equipment, without requiring expensive equipment investment and advanced technology establishment.

In this way, it is possible to supply materials stably for a long period of time without being affected by the circumstances of the importing partner country and price fluctuations. Further, the material of the present invention has an advantage in that it has excellent curl prevention and shape stability and high rigidity as compared with the conventional product because it has a punched and extruded laminated layer interposed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Hiroshi Kawahara, 4-13-18 Andachi, Suminoe-ku, Osaka City, Osaka Prefecture, Goyo Paper Works Co., Ltd. (56) References JP-A-51-33175 (JP, A) Open 62-240544 (JP, A) Open 63-47128 (JP, U)

Claims (3)

[Claims] 1. A laminated material for food container paper, characterized in that cardboard having a basis weight of 300 to 400 g / m ² is used, which is made by laminating a plurality of thin papers through a perforated extrusion laminated resin layer. 2. A perforated extruded laminated resin layer, wherein the adhesive resin is selected from a foaming agent, a filler and a tackifier.
1. A resin composition containing one or two or more species.
Laminated material for food container paper as described. 3. A food container paper laminate material comprising a cardboard sheet according to claim 1 and a laminate layer provided on one or both sides thereof.