JPS594668A - Bonding of paper or aluminum foil to resin - Google Patents

Abstract

PURPOSE:To improve blocking resistance and slippability, by coating on the surface of a paper, etc. an aqueous dispersion of a specific ethylene-vinyl acetate copolymer, then drying to form a discontinuous film, followed by bonding at a specific temperature a thermoplastic resin to said film. CONSTITUTION:On the surface of a paper (pref., a coated paper of 10-300mu thick) or an aluminum foil (pref., of 10-80mu thick), an aqueous dispersion of an ethylen-vinyl acetate copolymer with the minimum film-forming temperature of 50-90 deg.C[e.g., prepared by dispersing, using 2-35pts.wt. of a partially-saponified polyvinyl acetate as a dispersant, in 30-200pts.wt. of water, 100pts.wt. of an ethylene-vinyl acetate copolymer containing 5-50wt% of vinyl acetate] is coated so that its amount (as solid component) is 3-25g/m<2>, then dried to form a discontinuous film, followed by bonding the film to a thermoplastic resin (e.g. polypropylene with a melting point >=100 deg.C) at a temperature higher than the film-forming temperature mentioned above (pref. by 50 deg.C higher).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of adhering paper, aluminum foil, and thermoplastic resin, and a method of adhering paper, aluminum foil, and thermoplastic resin molded product.

BACKGROUND ART In order to decorate the surface of a thermoplastic resin molded product, it has been conventional practice to adhere a label (including a blank) to the surface of the molded product.

These labels are bonded by applying adhesive to the back of the printed label, drying if necessary, and then fixing this label in a mold by electrostatic adhesion or reduced pressure so that the printed side is in contact with the mold. Then, the label is adhered to the thermoplastic resin container by injection molding, blow molding, vacuum forming or pressure forming the melted thermoplastic resin.

It is still practiced to apply a solvent-based isocyanate-based prepolymer to the surface of printed paper, and then extrusion laminate a polyethylene film melted at 300° C. to impart water resistance to the paper.

Conventionally, in addition to the above-mentioned incyanate-based prepolymers, adhesives made by dissolving vinyl chloride/vinyl acetate copolymers in a solvent have been used as adhesives for paper and thermoplastic resins, but in recent years, food sanitation issues have arisen. , due to the problem of environmental sintering due to air pollution caused by solvents, alternatives to them were investigated, and an aqueous dispersion of polyolefin having acid groups as an adhesive (Japanese Patent Application Laid-Open No. 55-108
432) and an aqueous dispersion of ethylene/vinyl acetate copolymer (JP-A-56-106940, USP 3,7
No. 08.388, No. 3,925,289, No. 4,12
6°729, etc.) has been proposed.

Generally, aqueous dispersions of these resins are applied to the surface of substrates such as paper, aluminum foil, thermoplastic resin films, etc., and heated above the minimum film-forming temperature of the aqueous dispersion to impart water resistance and heat sealability. A continuous film is formed.

In order to form such a film on a substrate, it is preferable to use an aqueous resin dispersion having a low minimum film-forming temperature, but this has problems in terms of slip properties and anti-blocking properties.

In other words, if an aqueous dispersion of resin with a minimum film-forming temperature of 5 to 45°C is applied to the surface of paper and dried to a temperature above the minimum film-forming temperature to form a continuous film, the fabric is generally It is rolled up into a roll and stored in a warehouse, but during storage, the film and paper become blocked due to the rise in temperature inside the warehouse, especially in the summer, and after being rolled out of the warehouse, it is difficult to rewind it from the roll and use it. The base material is often damaged.

In addition, when this is used as a label, it is punched out with a die cutting blade, but the slipperiness is poor, so in order to improve the label's die blocking resistance and slipping properties, finely powdered silica or fatty acid amide is added to the aqueous dispersion. It is being added. However, the addition of these anti-blocking agents and lubricants is undesirable because it reduces the adhesive strength of the film. Further, when the resin of the aqueous dispersion is an ethylene/vinyl acetate copolymer having a high vinyl acetate content of 65 to 85% by weight, the effects of these antiblocking materials and lubricants are not exhibited.

The present invention was made for the purpose of improving such drawbacks of conventional aqueous dispersions of ethylene/vinyl acetate copolymers.
To solve this blocking problem, an aqueous dispersion of ethylene/vinyl acetate copolymer with a minimum film forming temperature of 50°C to 90°C is used as a dispersion liquid, and the film on the base material of paper or aluminum foil is made into a discontinuous film. The problem was solved by this.

That is, in the present invention, an aqueous dispersion of ethylene/vinyl acetate copolymer having a minimum film forming temperature of 50°C to 90°C is applied to the surface of paper or aluminum foil, and then dried to form a discontinuous film. The present invention provides a method for bonding paper or aluminum foil to a resin, characterized in that the discontinuous film and the thermoplastic resin are then bonded at a temperature equal to or higher than the minimum film forming temperature.

In carrying out the present invention, the base paper may include pulp paper,
In addition to washi paper, art paper, coated paper, and inorganic fillers are included in the range of 8 to 65.
Examples include synthetic paper made by stretching a thermoplastic resin film containing % by weight. The wall thickness of these materials is generally 10 microns to 300 microns.

Further, the thickness of the aluminum foil as another base material is generally 10 to 80 microns.

Next, the minimum film forming temperature (hereinafter referred to as MFTJ) is 50°C.
The aqueous dispersion of ethylene-vinyl acetate copolymer at ~90°C is prepared by using partially saponified polyvinyl alcohol 2 as a dispersant, for example, 100 parts by weight of ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 50% by weight. ~35 parts by weight is dispersed in 30 to 200 parts by weight of water using a twin screw extruder to obtain an aqueous dispersion with a MFT of 50 to 90°C (see JP-A-56-106940). .

In addition, acrylic acid, ethyl acrylate,
Aqueous dispersion of ethylene/vinyl acetate copolymer obtained using ammonium salt of butyl methacrylate copolymer (liquid)
(Japanese Patent Application No. 57-9566) can also be used. Also,
Instead of the ethylene/vinyl acetate copolymer, a copolymer graft-modified with maleic anhydride, acrylic acid, methacrylic acid, or an ester thereof may also be used (Japanese Patent Application Laid-Open No. 101845/1984).

Various adhesives such as petroleum resin, rosin, rosin ester,
Terpene resins, terpene-phenol copolymers, chlorinated polyethylene, etc., fillers such as paraffin wax,
Waxes such as microcrystalline wax and carnauba wax may be added. However, in this case as well, the amounts and types of these adhesives and extenders must be selected so that the MFT of the aqueous dispersion is 50 to 90°C.

If the MFT of the aqueous resin dispersion is less than 50° C., the anti-blocking properties of the resulting film will not be improved, leading to problems in label die-cutting properties and summer storage.

This aqueous dispersion of ethylene/vinyl acetate copolymer with an MFT of 50 to 90°C is applied on paper or aluminum foil using a roll, brush, spray, etc. from 3 to 25t7W? (solid content) and dried at a temperature below the MFT temperature, or dried by heating for a time that does not form a continuous film even at a temperature above the MFT, and used as adhesive decorative paper.

Generally, these are rolled up and stored before being bonded with thermoplastic resin for use as labels or decorative paper, but since the film on the base material is discontinuous, papermaking is more difficult than in the case of a continuous film. Since it has excellent blocking properties and the MFT of the aqueous dispersion is as high as 50° C. or higher, it is free from the problem of blocking.

Next, thermoplastic resins to be adhered to these labels, decorative paper, etc. include polyethylene, polypropylene, ethylene/propylene copolymer, polyvinyl chloride, polystyrene/Siimpact polystyrene, ABS, acrylonitrile/styrene copolymer. Generally, resins having a melting point of 100° C. or higher can be used, such as polyethylene terephthalate, polyamide, saponified ethylene/vinyl acetate copolymer, and polycarbonate.

Adhesion of labels, decorative paper, etc. and these thermoplastic resins can be achieved by various methods described below.

(1) A molten film of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, etc. is extrusion laminated on the discontinuous film of decorative paper and pressed with a cooling roll.

(2) Place the decorative paper on the pre-formed thermoplastic resin film so that the discontinuous film is in contact with the film, and then press with a hot roll to melt and adhere the discontinuous film. .

(3) Place the label so that the discontinuous film is in contact with the surface of a thermoplastic resin molded product, such as a film, container, or cabinet, and then press a heated iron onto the label to melt the discontinuous film. Glue.

(4) A method of injection molding, blow molding, pressure molding, or pressure molding a thermoplastic resin in a mold using static electricity or decompression means, and adhering the label to the molded product at the same time as the molding.

These adhesion processes are carried out at a temperature higher than the minimum film forming temperature of the resin aqueous dispersion, preferably at least 50° C. higher than the minimum film forming temperature.

If papermaking is carried out at a lower temperature than MFT, the adhesive strength between the label, decorative paper and thermoplastic resin molded product will be insufficient.

The molded articles obtained by carrying out the present invention are useful as shampoo containers, fancy toiletries, wallpapers, etc. The present invention will be described in detail below with reference to Examples.

In addition, the parts and % in the examples are based on the limited paper weight that does not particularly invert.

Label manufacturing example Polypropylene “Noprene MA-6” manufactured by Mitsubishi Yuka ■
Product name) 90 parts, high-density polyethylene “Yukalon Heart EY-40” manufactured by Mitsubishi Yuka ■ (Product name) 10 parts, titanium oxide with an average particle size of 1μ 0.8 parts, clay 15 parts, antioxidant 0.3 After melting and kneading a composition of 1 part and 0.1 parts of oleic acid using an extruder, it was extruded into a sheet at a temperature of 200°C from a gouer, and the sheet was cooled to about 50°C. Next, this sheet was heated to about 135° C., and then stretched four times in the longitudinal direction using the difference in peripheral speed between the roll groups.

Separately, polypropylene (Mitsubishi Noprene MA-6) 10
0 parts, 10 parts of titanium oxide with an average particle size of 1μ, and an average particle size of 1.
80 parts of 5μ calcium carbonate, bis(2,2,6,6-
A composition containing 0.4 part of tetramethyl-4-piperidyl), 3 parts of an antioxidant, and 0.1 part of oleic acid was melt-kneaded using two other extruders, and then put into a die. The longitudinally stretched sheet is laminated on both sides of the sheet at a temperature of 200°C, and then heated to 20°C from room temperature.
After cooling to a high degree of immersion, it is reheated to about 155°C, stretched 8 times in the transverse direction using a tenter, and then heat set by passing through an oven at 160°C to form the intermediate layer (base material layer). 2
A three-layer structure was printed in which the thickness of the axially stretched film was 70 μm, and the thickness of the uniaxially stretched films on the front and back layers was 10 μm each. A film with excellent writing properties was obtained. The surface of this composite film was treated with corona discharge treatment. Thereafter, an acrylic antistatic agent solution 5T-1300 manufactured by Mitsubishi Yuka Co., Ltd. was applied to the treated surface and dried.

Next, the edges of the composite stretched film are slit, and further,
The composite stretched film was cut into a width of 50 m using a knife cutter perpendicular to the film flow direction, and the cut composite stretched film was stored in a sheet stocker.

Multicolor offset printing was performed on the paper-like layer surface of the cut sheet-like synthetic paper according to the purpose.

Example 1 21.6 parts (0.3 mol) of acrylic acid, 30 parts (0.3 mol) of ethyl acrylate, 56 parts of butyl methacrylate
．． 8 parts (0.4 mol) and 1 part isopropyl alcohol
50 parts were placed in a 4-tube flask equipped with a stirrer, reflux condenser, thermometer, and dropping funnel, and after purging with nitrogen gas,
Polymerization was carried out at 80°C for 3 hours using 0.6 part of 2.2'-azobisisobutyronitrile as an initiator. Next, 28%
After neutralizing with 18.2 parts (0.3 mol) of ammonia aqueous solution, water is added to replace the isopropyl alcohol while distilling it off, and finally a viscous acrylic copolymer with a solid content of 30% is obtained. An aqueous solution of the neutralized product was obtained.

Ethylene/vinyl acetate copolymer (vinyl acetate content 28
%, melting point: 74°C, melt index at 190°C: 150 t/1o min) at a rate of 100 parts/hour using a co-rotating intermeshing twin screw extruder (Ikegai Tekko Co., Ltd. trade name: PCM45, triple thread shallow groove type, It was continuously supplied from a hopper with L/D=30).

Furthermore, 113.2 parts of water was added to the 26.8 parts (8 parts as solid content) aqueous solution of the neutralized product of the acrylic copolymer through the supply port provided in the vent part of the same extruder. thing 1
A gear pump (discharge pressure 3Kf/
A milky white dispersion was obtained by continuously extruding at a heating temperature (cylinder temperature, the same applies hereinafter) of 130° C. and a screw rotation speed of 100 rpm) while pressurizing and continuously supplying the mixture under pressure (dG).

The average particle size of this aqueous polymer dispersion was determined using a microscope and was approximately 3 microns.

Examples 2 to 6 Post-emulsified resin aqueous dispersions were produced under the same conditions as in Example 1, except that the various thermoplastic phases shown in Table 1 were used.

The average particle diameters of these dispersions were all 2 μm or less.

Example 7 Ethylene-vinyl acetate loaded combined pellets (
MI 12 y/x o minutes, melting point 85°C, vinyl acetate content 28% by weight) was continuously supplied at a rate of 80 parts/hour, and from the supply port provided at the vent part of the compression zone of the extruder. Partially saponified polyvinyl alcohol (Kuraray product Kuraray Boval, prototype, degree of saponification 75 mol%, degree of polymerization 20
50, melting point 168°C) 100 parts/100 parts/
Plunger pump (discharge pressure 3Kp/
It was continuously extruded at a heating temperature (Schilling temperature, the same applies hereinafter) of 90° C. while continuously supplying the mixture under pressure (dG).

The resulting extrudate was a milky white homogeneous dispersion, the average particle size of the resin in the dispersion was 2μ, and the MFT of the dispersion was 75°C.

Example 8 80 parts of the aqueous dispersion obtained in Example 3 above and 20 parts of the aqueous dispersion obtained in Example 6 were mixed at room temperature to obtain an aqueous dispersion having an MFT of 65°C.

Resin aqueous dispersion evaluation examples 1 to 8 The resin aqueous dispersions obtained in Examples 1 to 8 were coated on the back side of art paper with a wall thickness of 80μ using a bar coater so that the solid content was 10 f/n? After applying the coating to 110℃ for one day and night at the temperature shown in Table 1,
It was stored in a vacuum chamber of 1111IH to form a film.

The slip properties and anti-blocking properties of this film were evaluated using the following methods. The results are shown in the same table.

Slip property (ASTM D-1894-73): A sled with a load of 200 t is placed on the film and the sled is stretched for 150 m++
The coefficient of kinetic friction when pulled and moved at a rate of /min is 2
Measurement was performed at 3° C. and 65% RH.

Anti-blocking property: Overlap the uncoated side and coated side of art paper, 150m wide
A glass plate measuring 200 m in length was placed to cover this overlapping part, and a load of 15 to 9 was placed on top of it and placed in a room at 23°C, 50% RH or 50°C, 80% RH for 7 days. After standing, when the overlapping portion was peeled off, a case where the art paper was damaged was judged as poor anti-blocking property, and a case where the art paper was not damaged was judged as good anti-blocking property.

(Margins below) Example: The aqueous dispersion obtained in Example 1 was applied to the printed side of the synthetic paper that had been printed in multicolor offset in Example 1, and the solid content was 129/m2.
' After coating, it was dried at 60°C for 18 hours to form a discontinuous film.

Then, it was cut out to obtain a regular pentahedral blank with a side length of 50 mm.

After fixing this blank to the inner surface of the injection mold using reduced pressure, polypropylene (melting point 164°C) was heated at 240°C for 1 hour.
The container was injection molded at a pressure of 0.00 kg/- and cooled for 2 minutes to obtain a rectangular prism-shaped container (wall thickness: 2.0 mm) with decorations on the entire surface.

It was difficult to peel off the blank of this container by hand.

Example 2 10 y/n? of the resin aqueous dispersion obtained in Example 4 was applied to the back side of an 80 μm thick anide paper. (solid content) and dried for one day under the conditions of 60℃ and 10mmHf to form a discontinuous film.
Cut it into strips.

Using this strip as a label, heat the thermoplastic resin sheets shown in Table 2 at 60°C, 80°C, 120°C, 150°C, and 180°C.
At each temperature, a pressure of 2Kq/c++t was applied using a heat sealer for 1 second to bond five different widths.

Next, the heat seal strength was measured using an Autograph Model 15-2000 manufactured by Shimadzu Corporation at a tensile rate of 30011++1/min according to the method of JIS K-6854.

The results are shown in the same table.

* High impact polystyrene ** Polyethylene terephthalate * 3 Art paper destroyed Example 3 The art paper having the EVA discontinuous film obtained in Example 7 was cut into 20 mm long and 40 cm wide pieces as labels.

After inducing static electricity on this label and fixing the label in the female mold by electric attraction, a sheet made of high-density polyethylene [Yukaronno-de EY-4OJ (thickness 0.6+m)
After heating to 0° C. and introducing onto a mold, the tip was vacuum formed with the aid of a plug under reduced pressure of 45 mHg.

I tried to remove the label from the tip, but it was difficult and the art paper was destroyed.

Example 4 Art paper (with a discontinuous film of EVA obtained in Example 1 above)
Table 3 shows the results of adhering a high-density polyethylene sheet (with a drying temperature of 60° C.) and a high-density polyethylene sheet having a thickness of 1 layer at various temperatures in the same manner as in Example 2, and measuring the adhesion strength.

Comparative Examples 1-3, Examples 5-7 Said Examples 2.3.4 (Drying Temperature [60°C), 5.6 and 8
A label was prepared by cutting out the art paper having the resin film obtained in Example 2 into strips in the same manner as in Example 2, and the adhesiveness with the resin sheet shown in Table 3 was measured in the same manner as in Example 2.

The results are shown in the same table.

(Margin below)

Claims (1)

[Claims] 1) Apply an aqueous dispersion of ethylene/vinyl acetate copolymer with a minimum film forming temperature of 50°C to 90°C on the surface of paper or aluminum foil, and then dry to form a discontinuous film. Method 0 for bonding paper or aluminum foil and resin, characterized in that the discontinuous film and thermoplastic resin are bonded at a temperature equal to or higher than the minimum film forming temperature.