JPS606431A - Manufacture of cylindrical laminated film - Google Patents

Abstract

PURPOSE:To produce a cylindrical laminated film that is free from curl and excellent in transparency, by using crystalline thermoplastic resins that can provide a special relationship between an inner layer and an outer layer, and performing down-flow water-cooled inflation forming. CONSTITUTION:As a crystalline thermoplastic resin for an inner layer is used a resin having a melting point relatively higher, preferably 5 deg.C or more higher, than the crystalline thermoplastic resin for an outer layer. The resin for the inner layer, the resin for the outer layer and, if required, various additives are fed to an extruder 1, and after they are melted and mixed, they are introduced into a circular and a die 2. Then they are extruded downward and is subjected to down-flow water-cooled inflation forming (for example, blowing is effected by an air ring 3 and cooling water 4 is directly brought in contact with the bulb). The cooling temperature is 10-40 deg.C, and the blow-up ratio is 0.8-3. The layer thickness ratio of the outer layer to the inner layer is to be in the range of 30:70- 97:3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cylindrical laminate film, and more particularly to a method for manufacturing a cylindrical laminate film that has excellent transparency and prevents curling.

Conventionally, low-density polyethylene resins, polypropylene resins, and the like have been used in many fields because of their excellent mechanical properties and transparency.

However, when the cylindrical films obtained from these crystalline thermoplastic resins are produced by conventional top-blown air or cold ink injection molding, they do not have sufficient transparency, and their uses are largely limited. Therefore, attempts have been made to rapidly cool the molten resin film by bottom-blown water-cooled inflation molding. However, the more the rapid cooling effect is used to improve transparency, the more a difference in cooling between the inside and outside of the molten resin film occurs, causing large curls on the inside and blocking, making it impossible to use it as a film product. There is a problem. In particular, straight-lined low-density polyethylene, which has been attracting attention recently, has excellent transparency.
Moreover, a film that does not cause curling or blocking has not yet been obtained. On the other hand, a method has also been proposed in which a solid filler is added to the resin side, which has a higher molding shrinkage rate, in a laminated film, but although this method is effective in preventing curling, it has the disadvantage that it cannot satisfy the requirements for transparency. There is.

The present invention is a patent that is characterized by preventing the above-mentioned conventional drawbacks and providing a cylindrical laminated film that has excellent transparency and is free from curling and blocking.

That is, in producing a cylindrical laminated film consisting of at least two crystalline thermoplastic resin layers, the present invention uses a resin having a relatively higher melting point as the inner layer crystalline thermoplastic resin than the outer layer crystalline thermoplastic resin. The present invention provides a method for producing a cylindrical fall layer film, which is characterized by bottom-blown water-cooled inflation molding.

The crystalline thermoplastic resin used in the present invention is not particularly limited, and various resins may be used.

For example, high density polyethylene, medium density polyethylene.

Low-density polyethylene, copolymers of ethylene and other α-olefins, low-density low-density polyethylene with medium-low construction method, polypropylene (homopolymers, copolymers with other α-olefins, random copolymers).

Polyolefins such as polybutene-1 and poly4-methylpentene-1; nylon 6. Examples include polyamides such as nylon 66; polyesters.

The present invention uses the above-mentioned crystalline thermoplastic resin to produce a cylindrical laminated film consisting of at least two layers, the inner and outer layers, and the crystalline thermoplastic resins used as the inner and outer layers have a specific relationship. It is necessary to use

That is, as the crystalline thermoplastic resin for the inner layer, a resin whose melting point is relatively higher than that of the crystalline thermoplastic resin for the outer layer is used.

The crystalline thermoplastic resin for the inner layer may have a relatively higher melting point in relation to the crystalline thermoplastic resin for the outer layer, and is appropriately selected based on the melting point of the outer layer film used.

The melting points of the crystalline thermoplastic resins exemplified above are shown below.

The melting point of high-density polyethylene is usually 125-135°C1
The melting point of low density polyethylene is usually 110-130°C1
The melting point of polypropylene is typically 160-180''C, the melting point of nylon 6 is typically 225°C, the melting point of nylon 66 is typically 265°C, and the melting point of polyethylene terephthalate is typically 265°C.

Further, the melting point of the crystalline thermoplastic resin for the inner layer may be relatively higher than that of the crystalline thermoplastic resin for the outer layer, but it is preferably 5°C or more higher, more preferably 10°C or more higher. use something This is because under the temperature conditions for rapidly cooling and crystallizing the crystalline thermoplastic resin in the outer layer, the temperature of the inner layer is about 10 to 50° C. higher than that of the outer layer.

Furthermore, the layer thickness ratio between the inner layer and the outer layer is outer layer:inner layer=30:
It may be appropriately selected within the range of 70 to 97:3. If the ratio of the inner layer to the total layer is less than 3%, the formability of the film becomes difficult and the effect of the method of the present invention of preventing curling is not sufficiently achieved.

In addition, if necessary, a crystal nucleating agent may be added to the crystalline thermoplastic resin of the inner layer to increase the melting point or speed up the crystallization rate. By adding this crystal nucleating agent, it is possible to regulate the crystal nucleation rate of the crystalline thermoplastic resin, accelerate the crystallization rate, and at the same time suppress the size of the crystals. Such crystal nucleating agents include organic nucleating agents such as metal salts of organic acids, such as habenzoic acid, cyclohexanecarboxylic acid, diphenylacetic acid, isonicotinic acid, adipic acid, heptano(cynic acid, phthalic acid, benzene). Magnesium, calcium, sodium such as sulfonic acid, yvcholic acid.

Examples include metal salts such as aluminum and titanium; amine salts of organic acids, such as amines derived from ammonium, fragrant acid, phthalic acid, adipic acid, and the like. Examples of the inorganic nucleating agent include fine powders of silica, alumina, talc, and the like.

Further, another crystalline thermoplastic resin may be used as an intermediate layer between the inner and outer layers.

Furthermore, each crystalline thermoplastic disease layer contains various additives such as stabilizers (RA prevention agents, thermal decomposition inhibitors, etc.), anti-blocking agents, slip agents, colorants, fillers, etc. for the purpose of the present invention. It can also be added within a range that does not impair it.

The present invention is characterized in that a crystalline thermoplastic resin having a specific relationship as described above is used for the inner and outer layers, and is subjected to bottom-blown water-cooled inflation molding.

That is, first, the above crystalline thermoplastic resin used as the inner layer and the outer layer and various additives used as necessary are supplied to a known extrusion molding machine, melted and kneaded, and then introduced into a circular die. Then push it downwards,
Rapidly cool by bottom-blown water-cooled inflation molding. 1st
The figure is an explanatory diagram showing an example of bottom-blown inflation molding. Although a method of bringing the cooling water into direct contact with the bubbles has been shown here, a method of making the cooling water into a mist and melting it may also be adopted. In the figure, numeral 1 is an extrusion molding machine.

2 is a circular die, 3 is an air ring, 4 is a cooling water, and 5 is a laminated film. The temperature of the cooling water is usually 10 to 40"C, preferably 15 to 35C. The blowup ratio is usually 0.8 to 3, preferably 1.
It is 1 to 2.5.

In addition, in the method of the present invention, the optimum conditions may be determined by considering the above-mentioned cooling rate, the thickness ratio of one layer of the crystalline thermoplastic resin used, and the like.

As mentioned above, in the method of the present invention, a crystalline thermoplastic resin having a specific relationship is used for the inner and outer layers, and this is rapidly cooled by bottom-blown water-cooled inflation molding, so there is no curling at all and it has excellent transparency. It is possible to obtain a film that is The reason why curling can be prevented is not clear, but it is thought to be as follows. That is, it is believed that curling occurs because the crystalline thermoplastic resin in the inner layer crystallizes after the crystalline thermoplastic resin in the outer layer is rapidly cooled and crystallized, but according to the method of the present invention, curling occurs in the outer layer. Under the temperature conditions where the crystalline thermoplastic resin is rapidly crystallized and fixed, the inner layer is made of a crystalline thermoplastic resin that crystallizes at the temperature of the inner layer at that time, so the inner and outer layers are crystallized and fixed almost simultaneously. It is.

Furthermore, according to the method of the present invention, a film with no blocking and excellent opening properties can be obtained, and only a small amount of anti-blocking agent and the like can be added. Also,
The method of the present invention has superior productivity because it can cool the film more rapidly than conventional methods.

Therefore, the method of the present invention can be effectively used for manufacturing cylindrical laminated films used for various types of packaging.

Next, the present invention will be explained by examples.

Example Using two extruders with a diameter of 50 mm and an L car of 26, ethylene-octene-1 copolymer (density 0.927 g/crrt3. Melt index (MI) 4.99710 minutes) was used as the crystalline thermoplastic resin for the outer layer. , melting point 125℃)
, polypropylene (density o, 91 g/a, MI 79/1o min, melting point 170) was used as the crystalline thermoplastic resin for the inner layer.
°C) was fed into an extruder and melted and kneaded, then introduced into an in-die adhesive circular die (150 mrptφ, die lip gap 2 mm), extruded downward, and subjected to bottom-blown water-cooled inflation molding at a blow-up ratio of 1.3. A coextrusion laminated two-layer film having a thickness of 40 μm (outer layer: inner layer = 872) was produced by carrying out the following steps.

The obtained film had no curl at all and had a haze level of 2.1.
%, gloss of 152%, and excellent opening properties.

Comparative Example A monolayer film having a thickness of 40 μm was obtained in the same manner as in the Example except that only the ethylene-octene-1 copolymer used as the crystalline thermoplastic resin for the outer layer was used.

The resulting film had poor opening properties, and moreover, the opened 7-ilms were severely curled inward, making them completely unsuitable for use as a film.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of bottom-blown inflation molding. l...Extrusion molding machine, 2...Circular die. 3...Air ring, 4...Cooling water, 5...Laminated film Patent applicant Idemitsu Petrochemical Co., Ltd.

Claims (1)

[Claims] 1. In producing a cylindrical laminated film consisting of at least two crystalline thermoplastic resin layers, a resin having a relatively higher melting point than the crystalline thermoplastic resin of the outer layer is used as the crystalline thermoplastic resin of the inner layer, A method for producing a cylindrical laminated film characterized by bottom-blown water-cooled inflation molding.