JPS5839898Y2 - Improved packaging containers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a packaging container made from a paper-plastic laminate.

Currently, there are many packaging containers on the market that use laminated sheets made of paper with polyethylene laminated on one or both sides, and are extremely conveniently used for packaging foods (both solid and liquid).

However, this container made of a laminated sheet of polyethylene and paper has the following drawbacks, and improvements to these have been desired.

(1) Poor heat resistance.

Therefore, it is not possible to heat the food in its entire container in a microwave oven, and it is also difficult to sterilize the food at high temperatures.

(2) Odors are easily transferred.

This is because polyethylene easily transmits odors.

(3) Becomes brittle and easily broken at low temperatures.

(4) Poor oxygen barrier properties.

Therefore, there is a risk that the food inside may deteriorate or change color.

(5) Poor oil resistance.

(6) It is difficult to print on polyethylene surfaces.

The present invention significantly improves many of these drawbacks, while still retaining the good points (for example, heat sealability and transparency) that paper/polyethylene laminate sheet containers also have.

The gist of this invention is that polybutylene terephthalic acid (abbreviated as PBT) is laminated on at least one side of paper.
It is a container consisting of a layer or a laminate of three layers.

In other words, the container shown in FIG. 3 is made from a laminated sheet having a cross section as shown in FIG. 1 in the case of two layers, and as shown in FIG. 2 in the case of three layers.

In FIGS. 1 and 2, 1 is paper and 2 is a PBT layer.

Figure 3 shows an example of the container of the present invention, in which a tube with a square cross section is made from three-layer laminated sheets, both ends of which are covered with the same sheet, and the periphery is sealed by heat sealing and mechanical caulking. It is a tight box-shaped container.

The paper referred to in this invention may be natural paper, 9 synthetic paper, or mixed paper, but may include kraft paper (unbleached, @both), white paperboard,
Roll paper, imitation paper, glassine paper, etc. are easy to use, especially those with a basis weight of 50 to 400 g/m2, preferably 100 to 30 g/m2.
0 g/m2 is preferred.

If the basis weight is lower than this range, the resulting container will tend to have poor shape stability, while if the basis weight is higher than this range, the container will tend to lack flexibility.

PBT is a polyester consisting of 1,4-butanediol and terephthalic acid, but it does not necessarily have to be a homopolymer; it can be copolymerized with ethylene glycol, diethylene glycol, propylene glycol, isophthalic acid, adipic acid, sebacic acid, etc. It may also be a copolymer.

In particular, PBT copolymerized with 5 to 25 mol% of these components.
is suitable for the present invention because it has excellent extrusion lamination properties and processability.

However, in order to cook the entire container in a microwave oven, it is extremely desirable that the melting point of PBT be above 180°C, preferably above 200°C, so these points should also be taken into account when copolymerizing. It is desirable to select the composition appropriately.

Further, the intrinsic viscosity of PBT used in the present invention (measured in orthochlorophenol at 25° C.) needs to be in the range of 0.6 to 1.6, preferably 0.8 to 1.4.

If the intrinsic viscosity is lower than this range, the transparency will be poor, the container will be more likely to crack when bent, and it will become extremely brittle at low temperatures.

On the other hand, if the intrinsic viscosity is higher than this range, the adhesion to paper will be poor and the shape stability after molding will be poor.

The thickness of the PBT layer naturally depends on the basis weight and purpose of the paper, but it is usually in the range of 10 to 50 microns, particularly preferably in the range of 20 to 40 microns.

When laminating PBT layers on both sides of paper, the PBT layers on both sides
Preferably, the total thickness of the BT layers will be between 30 and 70 microns thick.

This PBT may contain approximately 0.01 to 1.0% by weight of known additives (for example, silica-based inorganic particles, etc.), and may also contain other known polymers (for example, ゛, polyethylene, terephthalate, etc.). or polycarbonate, etc.) to 0.
．． It may be blended in an amount of about 1 to 10% by weight.

By adding such additives and polymer blends, P
The BT layer may become slippery while maintaining transparency, and troubles such as blocking during handling can be avoided.

An example of the manufacturing method for the container of the present invention will be described below.

First, prepare the paper described above (for example, kraft paper).

This paper may be printed or plain.

This paper is extrusion laminated with molten PBT on one or both sides.

As the extrusion laminating device, a very common one frequently used for polyethylene lamination can be used as is.

There is usually no need to interpose anything between the paper and the PBT layer, but if necessary, a known anchor coating agent for promoting adhesion (titanate type, polyethyleneimine type, a mixture of urethane-modified polyester and polyisocyanate) may be used. system, a mixed system of melamine formaldehyde resin and self-crosslinking acrylic resin, etc.) may be used.

In this case, the anchor coating agent is thinly applied to the surface of the paper, dried, and then molten PBT is extruded and laminated thereon.

The finished laminated sheet of paper and PBT (printing may be applied to the PBT side) is bent, heat-sealed, or molded using conventional methods to form boxes, tetra packs, cups, and trays. FIG. 3 shows an example of a container having a desired shape, such as a two-bag shape, and the present invention is not limited thereto.

Of course, a container may be created by combining materials other than this laminated sheet.

Another method for producing a laminated sheet of paper and PBT is to prepare a PBT film separately in advance and bond this film and paper together using an adhesive, the so-called wet bond method or dry bond method. be.

However, this method of bonding using adhesive,
This method is far inferior to the extrusion lamination method described above because it tends to cause problems with the heat resistance, oil resistance, odor, etc. of the adhesive.

Furthermore, generally speaking, extrusion lamination can produce a laminated sheet more economically and cheaply than bonding with an adhesive, so extrusion lamination is more advantageous in this respect as well.

Finally, it should be mentioned that PBT is a material that is very specifically suitable for the packaging container of the present invention.

PBT is a polyester containing glycol with 4 carbon atoms, but polyester with 2 carbon atoms (polyethylene terephthalate).

(abbreviated as PET) and polyester with 6 carbon atoms (polyhexene terephthalate).

(abbreviated as PHT) are unsuitable for the present application.

The product using PET for the purpose of this invention cannot be put to practical use in terms of brittleness, cloudiness after heating, poor heat sealability, etc., and the product using PHT can withstand heating in a microwave oven. I don't get it.

Therefore, PET (2 carbon atoms) and PET (4 carbon atoms) differ only in the number of carbon atoms in the glycol among their constituent components.

Among PHTs (6 carbon atoms), only PBT is uniquely suited for this application.

The novelty of the present invention lies in the fact that this uniqueness of PBT is combined with the specific use of packaging containers.

An example will be described below, but the present invention is not limited to this example.

Example 1 White paperboard (basis weight 210 g/m2゜apparent thickness 0.3 m
PBT was melt-extruded laminated on both sides of (m).

A well-known melt extrusion laminating device that is frequently used for polyethylene was used as it was.

Thoroughly dried PBT resin (fixing viscosity 1.20°, copolymerized with 10 mol% isophthalic acid).

(melting point: 210°C) was supplied to an extruder having a 5-layer, mm-diameter screw, and melt-extruded at 280°C, cast into a sheet from a Karaslotive die, and laminated on one side of white paperboard according to a conventional method.

The same operation was performed on the opposite side of the white paperboard to obtain a laminated sheet with PBT laminated on both sides.

The thickness of the PBT layer on both sides was 25 microns.

The thickness of the resulting three-layer laminate sheet was therefore 350 microns.

This sheet was subjected to a bending process to make a rectangular parallelepiped-shaped container, into which the cooked curry was placed and sealed by heat sealing.

When I put this container in the microwave and heated it for 3 minutes and then took it out, I found that the container was not damaged in any way and the curry inside was sufficiently heated.

Moreover, this container was extremely excellent in odor and oxygen barrier properties and oil resistance and toughness, and also had a beautiful appearance with a transparent and glossy appearance.

Example 2 White paperboard (apparent thickness Q, 4 mm, basis weight 300 g/m
2) on one side of PBT resin (25% in 0-chlorophenol)
(intrinsic viscosity at °C: 0.98) was melt-extruded and laminated to a thickness of 10 microns in the same manner as in Example 1.

On the other hand, one side of an aluminum foil (thickness 12μ) was coated with a PBT copolymer (intrinsic viscosity at 25°C in O-chlorophenol: 1.
10. A product prepared by copolymerizing 15 mol % of isophthalic acid as a copolymer component) was melt-extruded and laminated to a thickness of 15 microns.

The paper and aluminum laminate thus obtained was
The above-mentioned melted PBT copolymer is sandwich-laminated in the middle layer with paper and aluminum facing each other to form PBT/paper/PBT copolymer/aluminum/PB.
A 5-layer laminate made of T copolymer was obtained.

This five-layer laminate product was formed into a tetra pack-like carton structure and filled with Japanese sake.

At this time, the side seam part and the volume seam part of the carton structure were partially folded so that the cross section of the five-layer laminate product did not come into direct contact with the sake, and was heat-sealed by blowing hot air.

After storing the carton containing the sake for 6 months in a thermostatic chamber maintained at 30°C and 66RH%, the taste, smell, etc. of the sake were tested, and there was no change in taste, smell, transparency, etc. It maintains excellent quality, no different from traditional bottled sake.

Example 3 A similar test was carried out by filling the cartons of Example 2 with soy sauce, milk, soy milk, liquid detergent, various juices, etc. instead of the sake, but there were no quality problems. Ta.

Furthermore, the carton of Example 2 was heated in advance (135~
Completely sterilized milk or juice is filled into a sterile paper container (acetic container) that has been steam sterilized at 138℃) and stored at room temperature (22℃, 60RH%) for 3 months.
When the quality of the milk and juice was checked, it was found that the milk and juice were stored in perfect condition, no different from before filling.

Comparative Example Polyethylene (Mirafun 451 Mitsui Petrochemical Co., Ltd.) was used instead of PBT and PBT copolymer used in Example 2.
When we conducted a similar test using , we obtained the results shown in the following table.

From the above results, it can be seen that PBT resin is superior to polyethylene in various respects as a resin for laminating with paper.

[Brief explanation of drawings]

Both FIG. 1 and FIG. 2 show cross sections of the laminated sheet for containers of the present invention, with FIG. 1 showing a case of two layers and FIG. 2 showing a case of three layers. FIG. 3 shows an example of the container of the present invention, which is a box-shaped container made of a three-layer laminated sheet. 1: Paper, 2: Polybutylene lentiphthalate F layer.

Claims (1)

[Scope of utility model registration request] A packaging container made of a laminated sheet of paper and polybutylene terephthalate having an intrinsic viscosity of 0.6 to 1.6.