JPS5915807B2 - How to make a container or bottle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing containers or bottles from thermoplastic polyester.

The purpose of the present invention is to prevent cracks caused by the filling contents in the non-oriented, amorphous parts of containers or bottles made from thermoplastic polyester, especially in the spout, especially solvent cracks under stress caused by filling with alcohol or other solvents. To provide a container or bottle that is highly durable and has a wide range of uses.

In recent years, attention has been focused on polyethylene terephthalate's excellent transparency, water vapor permeability, gas permeability, hygiene, and various well-balanced performances, as well as improvements in molding technology and demands for safety. In addition to films and injection molded products, carbonated beverage containers, seasoning containers, cosmetic containers,
Thermoplastic polyesters are also being used in remarkable ways in the field of containers and bottles, such as pharmaceutical containers.

5 However, in the case of hollow molded products such as containers or bottles,
Due to the purpose of filling the container or bottle, an inner lid is placed on the spout of the container or bottle to prevent leakage of the filled contents, for convenience of use, or to block contact with air during storage. In this case, the cap of the container or bottle is subject to considerable pressure from the lid, and if the contents to be filled contain solvents such as ethyl alcohol, stress cracks may occur, which will only spoil the aesthetics. However, it often cracks and cannot withstand long-term use15.
Currently, it is necessary to limit the scope of its use because it has a fatal drawback.

Direct blowing, injection blowing, biaxial stretching blowing, etc. are known as methods for manufacturing containers or bottles by blow molding, but polyester containers or bottles obtained by these methods are Both have the problem of solvent cracking under stress as described above. As a result of various investigations into the cause of this problem, the present inventors found that even in polyester containers or bottles manufactured by any of the above-mentioned molding methods, the spout part is not molecularly oriented and is substantially non-oriented. It was discovered that the clutch is composed of a crystalline part and is therefore susceptible to the diffusion and penetration of solvents, causing clutching under stress.As a result of intensive research into ways to prevent this, the method of the present invention was arrived at. That is,
In the present invention, when manufacturing a container or bottle using a thermoplastic polyester by blow molding, the solubility parameter of the Parylin spout before blow molding or the spout of the container or bottle after blow molding is 8.0 or less. Characterized by treatment with a solvent having a value of 12.0 than 35. When using the method of the present invention, no special equipment is required, and solvent cracking under stress can be effectively prevented by simple operation and short processing time.

Furthermore, the method of the present invention can be applied after the container or bottle is molded, and it is also important that it can be applied in the preform state, that is, the parison state, in injection molding, biaxial stretch blow molding, etc. This is an advantage. Thermoplastic polyester as used in the present invention means a crystalline aromatic polyester that provides transparent molded products.
Preferably, 80 mol% or more of the acid component is terephthalic acid, and other acid components include isophthalic acid and diphenyl ether. -dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, sebacic acid, etc., and 80 mol% or more of the glycol component is ethylene glycol, and other glycol components include propylene glycol, 1,4 - May contain butanediol, neobentyl glycol, diethylene glycol, polyethylene glycol, polytetramethylene glycol, cyclohexanedimethanol, bisphenol A1, bisphenol A with alkylene oxide, P-hydroxybenzoic acid, etc. Examples include polyester.

Further, the solubility parameter (δ) of the solvent used in the present invention is expressed as the square root of the cohesive energy density of the solvent, and the unit is (a〆t)%.

The solubility parameter of the solvent used in the present invention needs to have a value of 8 to 12 at 25°C, preferably 8.5 to 11. Moreover, the boiling point of the solvent is 15
It is particularly preferable that the temperature is 0°C or lower, and specific examples include acetone (δ = 10.0), methyl ethyl ketone (δ = 9.3), ethyl acetate (δ = 9.1), and dioxane (δ = 9.9). ), ketones such as benzene (δ=9.2), esters, ethers, aromatic hydrocarbons, and halogenated hydrocarbons. Note that high-boiling point solvents and solvents with phenolic hydroxyl groups are inferior to low-boiling point solvents because they cause hygienic problems as the solvent remains in the molded product after treatment, and they cause polyester to swell and dissolve. .

Usually, as is known from examples such as cosmetic bottles, pharmaceutical bottles, beer bottles, etc., most bottles have a narrow part from the mouth to the neck, and the body part has a length and swell depending on the amount of contents filled. ing. Examples of mechanical methods for producing bottles with such shapes from thermoplastic polyester include hollow molding or blow molding, including direct blow, injection molding,
It can be molded by any molding method such as biaxial stretching blowing.

In the case of a bottle molded by direct blowing using polyethylene terephthalate, the density of each part of the bottle is about 1.336 to 1.341, and the degree of crystallinity is 0 to 5%, which is essentially amorphous. Consists of quality. On the other hand, when a bottle is molded by injection molding or biaxial stretch blowing, a parison with or without a bottom is first preformed by injection molding or extrusion molding before blow molding. The parison at this time is also substantially entirely composed of amorphous material, which is then blown and stretched in a mold at an appropriate temperature to form the shape of a bottle. that time,
The degree of crystallinity and orientation of the body of the bottle improves considerably during the stretching process, but since the stopper of the bottle is fixed to the blow molding machine, there is almost no increase in the degree of crystallinity or orientation. The degree of crystallinity and orientation of the spout generally remains the same after blow molding as in the parison. Regardless of whether the bottles are molded by direct blowing, injector pro-1, or biaxial stretch blowing, the common point is that the mouthpieces of the bottles are hardly crystallized or oriented. ing. In the present invention, the container or bottle thus formed is treated with the above-mentioned solvent in the final step after molding, or in the form of a preform, that is, a parison before being expanded with compressed gas in the case of in-die extension processing or biaxial stretching blowing. The treatment improves the resistance to solvent cracking, especially under stress.

It is usually preferable to directly immerse only the spout of the container or bottle in the solvent for the above solvent treatment, but it is also possible to treat by applying or spraying the solvent on the front and back sides of the spout. You can also do that. In addition, the treatment time with a solvent varies depending on the type of solvent used, treatment power method, treatment temperature, desired solvent crack resistance, etc., but it may be carried out within a range that matches the commercial production cycle and is not particularly limited. It's not something you can do.

Sufficient solvent crack resistance can usually be obtained by surface treatment for several minutes to several tens of minutes. Further, there are no particular restrictions on the treatment temperature, but it is usually preferred to carry out the treatment at room temperature to mild temperature conditions. Note that although the spout of a container or bottle manufactured by the force method of the present invention becomes somewhat milky due to crystallization during solvent treatment, the spout was originally made of an opaque polyolefin inner lid or inner stopper. Since the outer cover and stopper are made of opaque or colored polyolefin area resin, the milky white appearance does not reduce the product value in any way. The container or bottle thus obtained has significantly improved resistance to solvent cracking under stress caused by the inner and outer stoppers, which improves the durability of the container or bottle and enables its use in a wide range of applications. It has great advantages in industrialization.

The present invention will be explained below with reference to Examples.

In addition, the inherent viscosity of the polyester in the examples is a value measured at 30° C. in a mixed solvent of parachlorophenol and tetrachloroethane at a weight ratio of 3:1. Example 1 A transparent cosmetic bottle with a narrow neck was molded using polyethylene terephthalate having an intrinsic viscosity of 1.05 using an injection molding machine Nectar SB15D/75 manufactured by Sumitomo Heavy Industries, Ltd.

In addition, the total length of the bottle is 125W! l, the length of the neck including the spout is 25mm, the length of the body is 10071gt, the inner diameter of the spout is 20711R1, the outer diameter is 25S111
The wall thickness is 2.5mm, the inner diameter of the body is 40WI, and the outer diameter is 42.
It is 77!11l. The resulting bottle was inverted and immersed in acetone (δ=10.0) for 10 minutes so that only 15 pieces of the spout were immersed. When taken out after 10 minutes, the acetone soaked area was slightly white.

After the acetone treatment, the bottle was air-dried for 20 minutes in the atmosphere, filled with ethyl alcohol, and a concave inner stopper made of polyethylene was fitted into the mouth of the bottle.

The outer diameter of the inner stopper is 0.5 mm larger than the inner diameter of the bottle cap, and the depth into which it is fitted into the bottle cap is 10 mm.

The mouth part of the bottle is constantly under pressure due to the inner stopper being fitted. The bottle with the inner stopper fitted was immediately turned upside down and left in such a way that the filled ethyl alcohol came into contact with the spout under pressure. The cap of the acetone-treated bottle showed no clutter or any change even after one week in an atmosphere of 30°C. Comparative example 1. The bottle molded in Example 1 was directly filled with ethyl alcohol without being treated with acetone. After inserting the inner stopper in the same manner as above, when the bottle was placed upright, numerous microcracks were generated in the mouth part of the bottle, which was almost instantaneously exposed to the pressure of the inner stopper.

Example 2. and Comparative Examples 2-3. Example 1. The bottle molded in Example 1. Ethyl acetate (Example 2.) and n-pentane (Comparative Example 2.) were used instead of acetone.
) and methyl alcohol (Example 3.). The crack resistance was examined in exactly the same manner as above.

The results are summarized in Table-1.

As is clear from Table 1, the pretreatment of the present invention dramatically improves the solvent cracking resistance of the bottle cap under stress.

Furthermore, it can be seen that pretreatment solvents whose solubility parameter (δ) is outside the range of the present invention have little effect on improving the solvent crack resistance. Example 1. The crack resistance was examined in the same manner as in Example 1, except that the immersion time of the acetone treatment was changed to 1 minute, 5 minutes, 7 minutes, and 7 minutes.

The results are shown in Table-2. Whereas bottles that are not treated with acetone tend to crack at the same time as they are under stress.
Solvent crack resistance was significantly improved even after a very short acetone treatment.

Example 4. A polyester having an intrinsic viscosity of 0.62 obtained by a conventional melt polymerization method and having repeating units of ethylene terephthalate/ethylene isophthalate (9/1 mole) was further heated in a blender at 190°C under a reduced pressure of 0.1 molar. A high degree of polymerization polyester having an intrinsic viscosity of 0.91 was produced by solid phase polymerization.

Claims (1)

[Scope of Claims] 1. When manufacturing a container or bottle using a thermoplastic polyester by blow molding, the solubility parameter of the spout of the parison before blow molding or the spout of the container or bottle after blow molding is determined. A method for producing a container or bottle, characterized in that it is treated with a solvent having a value of 8.0 to 12.0. 2. The manufacturing method according to claim 1, which uses a solvent having a boiling point of 150° C. or lower.