JPS60253511A - Manufacture of multilayer-tubular material for bottle - Google Patents

Abstract

PURPOSE:To obtain a multilayer bottle which does not generate ply separation and is superior in appearance, by a method wherein a multilayer-tubular material having multilayer structure made of a polyethylene terephthalate resin is heat-treated under specific terms after the same has been molten, extruded, vacuum-molded and quenched. CONSTITUTION:A multilayer-tubular material having multilayer structure made of at least a polyethylene terephthalate resin layer/a saponified article layer of ethylene- vinyl scetate copolymer whose ethylene contect is more than 25-55mol% and a sponification degree of an ingredient of vinyl acetate is more than 96mol% and the polyethylene terephthalate resin layer is heat-treated under terms satisfying an expression after it has been molten, extruded, vacuum-molded and quenched. In the expression: t1 is a larger side value between (-6T+390)min and 2min, t2 is a smaller side value between (-6T+630)min and 120min, (t) is heat treatment period (minute), and T is heat treatment temperature ( deg.C). Ply separation positions in a spotted state are not existed substantially on a multiclayer bottle molded on the multilayer-tubular material to be obtained with this constitution even if an observation of a trunk part is performed in detail and ply separation is not generated substantially even if the multilayer bottle is used as a container of carbonated beverage under a pressed state.

Description

DETAILED DESCRIPTION OF THE INVENTION A1 Technical Field of the Invention The present invention relates to a multilayer tubular body suitable for a multilayer bottle.

B. Prior art and its problems Biaxially stretched and oriented hollow bottles made of polyethylene terephthalate resin have poor mechanical strength, gas barrier properties, transparency,
Due to its excellent properties such as chemical resistance, it has made remarkable inroads into the food packaging and kitchenware fields, and has been used in containers for soy sauce, sauces, dressings, cooking oil, and dish detergent.

However, as demand for transparent containers with even higher gas barrier properties became stronger, polyethylene terephthalate resin and saponified ethylene-vinyl acetate copolymer (hereinafter referred to as E
A multilayer bottle made of VOH resin (denoted as VOH resin) has been proposed. When performing multilayer bottle molding by biaxial stretch blow molding, it is necessary to mold a multilayer preform by injection molding or extrusion molding. In general, the adhesiveness between polyethylene terephthalate resin and EVOH resin is low, and even when a multilayer bottle is molded, peeling easily occurs, deteriorating the appearance of the bottle.Therefore, there is a method of using adhesive resin to prevent peeling between the layers. Although this proposal has been proposed, if the preform is left undisturbed after molding, even if adhesive resin is used, peeling will occur between the layers of polyethylene terephthalate resin and adhesive resin, or between the layers of EVOHfM resin and adhesive resin. do. The degree to which peeling occurs varies depending on the type of adhesive resin used, but once peeling occurs, even if a multilayer bottle is molded, the peeled part remains without being reattached, making it impossible to obtain a multilayer bottle with a good appearance. The present invention was developed as a result of various studies aimed at solving the problems in molding multilayer bottles.

C1 The structure, purpose, and effect of the present invention, that is, the present invention provides at least polyethylene lid resin Na
A multilayer tubular body having a multilayer structure consisting of a saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 25 to 55 molti and a saponification degree of vinyl acetate component of 96 molti or more/a polyethylene terephthalate resin layer was melt-extruded, vacuum-formed, and rapidly cooled. Then, the following formulas (1) and (2) 50≦T≦100 (1) tl ≦t≦t 2 (2> However, tl is the larger value of (-6T+390) minutes and 2 minutes, t2 is (- 6'l'-1-630) minutes and 120 minutes, whichever is smaller, t: heat treatment time (minutes) T: heat treatment temperature (°C) This is a method for manufacturing a tubular body.

An object of the present invention is to produce a multilayer tubular body that does not cause delamination between layers and provides a multilayer bottle with an excellent appearance.
The multilayer tubular body according to the present invention does not cause peeling between the eyebrows of the pipe even if left for a long time after molding, and is suitable for molding multilayer bottles.

D1 More detailed description of the present invention The method of heat treating the multilayer tubular body after quenching in the present invention includes a method of quenching the tubular body and then continuously passing it through hot water for heat treatment, a hot water shower, etc. A method of heat treatment by passing through a hot air oven, a method of heat treatment by irradiation with infrared rays, or a method of cutting the multilayer tubular body after quenching to a convenient length for subsequent handling, and then immersing it in hot water. A method of heat treatment, a method of heat treatment in a hot air oven,
Some examples include a method of heat treatment by blowing steam.

The heat treatment time varies depending on the heat treatment temperature, as shown in equation (2), but should be at a level that does not cause peeling of the multilayer tubular body after the treatment. The heat treatment time is (-1'p+59
0) minutes or (-6'l'+650)
If it is too long, peeling may occur, which is not preferable.

The heat treatment temperature is preferably in the range of 50 to 100°C.

Treatment at temperatures as low as 50° C. is not preferable as it is not substantially effective as peeling occurs in the multilayer tubular body even after long-term heat treatment. On the other hand, treatment at temperatures above 100°C is effective in preventing peeling, but may cause the multilayer tubular body to soften and deform, and the polyethylene terephthalate resin layer or
Crystallization in the VOH resin layer is promoted, whitening of the multilayer tubular body occurs, and blow molding processability deteriorates, which is undesirable. Considering the effect of heat treatment, workability after treatment, etc., the heat treatment temperature is preferably within a range that satisfies formulas (1) and (2). These heat treatments do not require any special equipment, and commonly used hot water tanks, hot air dryers, etc. can be used.

Peeling as used in the present invention refers to a phenomenon of poor adhesion between layers that occurs between layers and does not disappear even after blow molding, and is a phenomenon of poor adhesion that occurs in a continuous belt-like direction in the pipe axis direction or a discontinuous spot-like poor adhesion. An example of this is the phenomenon.

The heat treatment may be carried out in a heated liquid above the water line, but in this case it is desirable to select a liquid that is easy to handle and does not leave any adverse effects on the appearance and moldability of the multilayered tubular body. Water, other liquids and gases used for heat treatment contain colorants,
Bactericides, fragrances, and other additives may also be added.

In forming a multilayer tubular body, vacuum forming and cooling are necessary methods to obtain a multilayer tubular body with a stable shape. The molten resin immediately after being extruded from the goo for a multilayer tubular body has fluidity and does not have shape retention. In order to obtain a multilayered tubular body with a stable shape, it is necessary to mold the resin into a certain shape until it develops shape-retaining properties, and the vacuum forming method is a molding method devised for this purpose. This method involves reducing the pressure on the outer surface of the resin using an oil rotary pump, water jet pump, etc. while the resin is passing through the tube, which is larger than the outer diameter of the tubular body, and bringing the resin into close contact with the tube wall from the inner surface. This process absorbs heat from the resin, imparts shape retention, and produces a multilayer tubular body with a stable shape. A high vacuum is rather undesirable since it is sufficient to apply pressure outward to the extent that no annular scratches occur on the outer surface of the tubular body. However, if the vacuum is lower than 75511IH9, it becomes difficult to obtain a stable shape, so this is also not preferable.

The inner surface of the multilayer tubular body immediately after vacuum forming has not yet been sufficiently cooled, but if slow cooling is performed instead of rapid cooling after vacuum forming, the crystallinity of the EVOH resin layer and polyethylene terephthalate resin layer of the multilayer tubular body will decrease. Problems such as large pores, whitening of the multilayer tubular body and decreased transparency, and a decrease in blow moldability due to the non-uniform stretchability of the EVOH resin layer occur when molding a multilayer container. In order to prevent the occurrence of such problems, rapid cooling is necessary, and in order to perform rapid cooling, it is preferable to spray water at a temperature of 60° C. or lower in the form of a mist onto the multilayer tubular body. It is important to rapidly cool the resin to below the crystallization temperature of each resin constituting the tubular body, and the multilayer tubular body that has been cooled to below the crystallization temperature may be cooled with water at 50° C. or below.

The multilayer tubular body according to the invention can be used in multilayer bottles as described above. An example of a method for forming a bottle from a tubular body will be briefly described below.

First, heat the appropriate length to form the multilayer preform. After that, a metal rod with a hemispherical tip that is slightly narrower than the inner diameter of the tubular body is placed inside the tubular body, and the tubular body is pushed into a mold that has a hemispherical hole with a diameter of 24.8flφ and a resin relief hole in the center. The tubular resin is condensed and held down by the inner metal rod to form a bottom with uniform thickness. After forming the bottom,
It may be cooled with cold water or air to prevent whitening due to crystallization of the resin at the bottom.

Next, the opposite end of the tubular body is heated within a range of 2.51 mm from the end to make the resin flexible, and the multilayer tubular body is inserted into a mold that can be divided into two parts provided with a threaded part. A mold for forming the shape of the inner surface of the neck is inserted into the interior under pressure to form a neck having a threaded portion. At this time, it is preferable to slightly stretch only the neck portion, and then blow pressurized fluid to bring the resin layer into close contact with a mold that forms the outer surface of the neck portion, thereby forming a biaxially stretched neck portion.

Next, the multilayer preform is rotated and heated until the temperature reaches 100°C to 130°C. If the heating time is prolonged, the crystallinity of the resin will increase and the blow moldability will decrease, so it is preferable that the heating time be as short as possible.

The multilayer preform, which has been heated and made flexible, is placed in a mold that can be divided into two or more parts of the desired shape, and a pressurized fluid such as pressurized air, pressurized nitrogen gas, etc. is blown into the preform to form the multilayer preform. Shape the bottle.

As for the bottle molding equipment, we used the same equipment that was developed for molding single-layer polyethylene terephthalate resin bottles.
It is possible to use it.

The saponified ethylene-vinyl acetate copolymer used in the present invention is a resin with an ethylene content of 25 to 55 mole and a degree of saponification of the vinyl acetate component of 96 mole or more, and the effects of the present invention are most pronounced in areas with low ethylene content. However, if the ethylene content is 25 moles, the moldability will decrease.
Satisfactory molding becomes difficult. Also, the ethylene content is 55
If the amount exceeds 10%, the gas barrier properties will decrease due to the increase in ethylene content, making it impossible to maintain satisfactory barrier properties. Moreover, if the degree of saponification is less than 96 molty, the gas barrier properties will be poor and it will not be possible to use it suitably in the present invention. The saponified ethylene-vinyl acetate copolymer can contain a sixth component other than ethylene, vinyl alcohol, and vinyl acetate units within a range that does not significantly affect barrier properties and moldability.

The polyethylene terephthalate resin in the present invention is
A polyester resin mainly composed of ethylene glycol and terephthalic acid, with an acid component of 80 molt or more, preferably 1 d
A polyester resin in which 90 moles or more is terephthalic acid, 70% or more of the glycol component, preferably 90 moles or more is ethylene glycol, and other acid components include inphthalic acid, phthalic acid, naphthalene 1, 4 or 2 degrees. 6-dicarboxylic acid, diphenyl ether 4.4
Aromatic dicarboxylic acids such as dicarboxylic acid, diphenyl dicarboxylic acid and diphenoxyethane dicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sepatic acid azelaic acid and decane 1,10-dicarboxylic acid, cyclohexane dicarboxylic acid, etc. Examples include alicyclic dicarboxylic acids such as acids. These can be used alone or in combination of two or more, and mixed with terephthalic acid in an amount less than 2C mole of the acid component.

Other glycol ingredients include propylene glycol,
trimethylene glycol, tetramethylene glycol,
Aliphatic glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol and neobentyl glycol, alicyclic glycols such as cyclohexipundimethanol, 2,2-bis( Examples include 4'-β-hydroxyethoxyphenyl)propane and other aromatic diols. These glycols can be contained within the glycol component in an amount of less than 20 mol.

The polyethylene terephthalate resin used in the present invention contains polyfunctional components such as trimethylolpropane, pentaerythritol, trimellitic acid, and trimesic acid.
Molty, preferably less than 3 moles, may be copolymerized.

In addition, colorants, antioxidants, ultraviolet absorbers, antistatic agents,
Additives such as antibacterial agents and lubricants can be contained in appropriate amounts as necessary.

In the present invention, it is often preferable to provide an adhesive between the inner and outer polyethylene terephthalate resin layers and the intermediate EvOH layer, and in this case, it is preferable to use an adhesive that has adhesive properties for both. For example, carboxyl group-modified polyolefin, carboxyl group-modified ethylene-ethyl acrylate copolymer, carboxyl group-modified ethylene-vinyl acetate copolymer, modified styrene-butadiene copolymer latex, polyacrylate,
It is possible to use polyurethane, and furthermore, polyester in which aluminum element and monocarboxylic acid are bonded as described in Japanese Patent Application No. 57-225426.

The multilayer bottle formed from the multilayer tubular body obtained by the method of the present invention has virtually no spot-like delamination spots even when the body is closely observed, and can be used as a container for carbonated beverages under pressure. Even when used, there is virtually no peeling between the eyebrows.

This point is one of the characteristics of the multilayer bottle using the tubular body produced by the method of the present invention.

The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto.

Example 1 Polyethylene terephthalate resin (melt flow index 1.5'/1o min at 270°C, melting point 265°C
) and an EVOH resin with an ethylene content of 32 molt, an EVOH resin with a saponification degree of 99.5 molt and a melt flow index of 0.7'/1o min at 190°C, and an adhesive resin with a vinyl acetate content of 24% by weight, A modified ethylene-vinyl acetate resin with a maleic anhydride modification degree of 1.1% by weight was fed to five extruders, and the ζEVOH resin was heated at 220°C.
The polyethylene terephthalate resin is melted and kneaded at a temperature of 278°C, and the adhesive resin is melted and kneaded at a temperature of 215°C.
Polyethylene terephthalate resin layer (thickness 1.sMII) z' adhesive resin layer (
Thickness o, 11m) / EVOH resin 71 (thickness [
o, s mm)/adhesive resin layer (thickness 0.1 fl
)/polyethylene terephthalate resin layer (thickness 1.5f
f) Extrude the multi-layered pipe of 3 types and 5 layers, immediately vacuum form it and rapidly cool it (with shower water) to make the pipe diameter 25f.
A multilayer pipe with an inner thickness of 3.5 mm was made. Pickup speed j, 5
After taking it off at %-, the pipe was cut into a length of 140 fl,
The cut pipes were sequentially immersed in hot water at 70°C and heat treated for 30 minutes. The pipe that had been removed from the hot water was left at room temperature for 30 days, but no peeling occurred in the multilayer pipe that would adversely affect the appearance of the multilayer bottle.

A multilayer preform prepared by sealing one end of this pipe and attaching a neck to the other end was heated to 105°C and then blow-molded using pressurized nitrogen. The obtained multilayer bottle was closely observed, but no peeling between the eyebrows was observed.

Example 2 A multilayer pipe manufactured in the same manner as in Example 1 was cooled for 70 minutes after being rapidly cooled.
The cod was cut into lengths and heat treated in a hot air dryer at 80°C for 20 minutes. Thereafter, it was cut again at 140111 and left at room temperature for 10 days, but no peeling occurred between the layers of the multilayer pipe. A multilayer preform prepared by sealing one end of this pipe and necking the other end was heated to 105°C, and then blow-molded using pressurized air. The obtained multilayer bottle was closely observed, but no peeling between the layers was observed.

Comparative Example 1 A multilayer pipe was manufactured in the same manner as in Example 1, but when the multilayer pipe was examined after being stored at room temperature for 7 days without heat treatment, numerous spot-like peeling spots were observed between the layers. . A preform was molded from this multilayer pipe, and a multilayer bottle was formed by biaxial stretch blow molding, but there were many spot-like peeling spots on the body of the bottle, and a multilayer bottle with a good appearance could not be obtained. .

Comparative Example 2 After extruding a multilayer pipe in the same manner as in Example 1 and rapidly cooling it, 12
When heat treated in a hot air oven at 0°C for 5 minutes, a portion of the pipe was deformed, which hindered the molding of the multilayer preform, resulting in a multilayer pipe that was unsuitable for use in multilayer bottles.

Claims (1)

[Claims] (1) At least a polyethylene terephthalate resin layer/
A multilayer tubular body having a multilayer structure of a saponified ethylene-vinyl acetate copolymer layer/polyethylene terephthalate resin layer with an ethylene content of FRZ 5 to 55 molar and a saponification degree of vinyl acetate component of 96 molar or higher was melt-extruded, vacuum-formed, and rapidly cooled. Then, the following equations (1) and (2) are used: A multilayer bottle for a bottle characterized by heat treatment under conditions satisfying the smaller value of 6'l'+6.!in) minutes and 120 minutes, where t: heat treatment time (minutes) T: heat treatment temperature ('C) Method for manufacturing a tubular body.