JPH06136160A - Coating fluid for protecting saturated polyester primary molding - Google Patents

Abstract

PURPOSE:To obtain a coating fluid which forms a protective film for preventing a saturated polyester primary molding being scratched and which can volatilize and does not remain in the product when the primary molding is heated again by forming a solution containing a specified amount of a specified compound. CONSTITUTION:The coating fluid comprises a solution (e.g., aqueous solution) containing 0.01-60wt.% compound of the formula: HO-(R-O)n-H (wherein R is 1-4C alkylene; and n is 10-10000). For example, this fluid is applied from the neck 3 of a primary molding 2 to its lower part to form a protective film 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prevention of scratches on a primary molded product in the process of producing a saturated polyester container by a biaxial centrifugal blow molding method. More specifically, the present invention relates to a coating liquid for forming a protective film on a primary molded product, a primary molded product having the protective film, and a biaxial stretch blow molding method for a saturated polyester container accompanied by application of the coating liquid.

[0002]

2. Description of the Related Art In biaxial stretch blow molding of a saturated polyester container, a bottomed primary molded article that has been injection molded and cooled in advance is reheated with an infrared heater or the like, and the reheated primary molded article is It is carried out by sending a pressurized fluid to.

By the way, the primary molded product is stored in a container or the like, aligned and sent to the reheating process. When the primary molded product is aligned and fed, the primary molded product comes into contact with the guides or the like of the aligning device. The surface of the is scratched, and the scratches become more conspicuous by being biaxially stretched, and the commercial value of the obtained product is impaired. In particular, in the case of a saturated polyester container, the presence of such scratches is conspicuous and the commercial value is likely to be lost because of its high transparency.

In order to prevent the occurrence of such scratches, conventionally, the scratches are removed by roasting the primary molded product with a burner flame and melting the surface of the primary molded product before reheating.

[0005]

However, in the heating by the above-mentioned conventional burner, in addition to the fuel cost of the burner leading to the high cost of the product, the variation of the flame of the burner is caused during the heating by the infrared heater. Since it is much larger than the uneven heating, there is a problem that the variation of the obtained products becomes large.

The present invention has been made in view of the above-mentioned problems of the prior art. It is intended to prevent scratches from being formed on the surface of a primary molded article, rather than eliminating scratches once formed such as surface melting by a burner. To aim.

[0007]

Therefore, in the invention of claim 1, the compound represented by the following formula (I) is
A solution containing 01 to 60% by weight is used as a coating liquid for protecting a saturated polyester primary molded product.

HO- (RO) _n -H (I) wherein R is alkylene having 1 to 4 carbon atoms and n is an integer of 10 to 10,000.

The invention of claim 2 is a saturated polyester primary molded article having a protective film as a film formed by coating and drying the coating solution, and the invention of claim 2 is saturated with the coating of the coating solution. This is a biaxially stretch blow molding method for polyester containers.

To further explain the present invention, the compound represented by the formula (I) includes polymethylene glycol, polyethylene glycol, polypropylene glycol, polyisopropylene glycol, polybutylene glycol, polyisobutylene glycol, poly t-butylene glycol and the like. Polyglycols, preferably polyethylene glycol and polybutylene glycol.

In the formula (I), n is an integer of 10 to 10,000, preferably 3000 to 9000. If n is too small, it is difficult to form a sufficient protective film, and the surface of the primary molded product is likely to be insufficiently protected. If n is too large, polyglycols are likely to remain on the surface of the product after reheat blow molding.

The solvent for the polyglycols may be any solvent which can dissolve the polyglycols in which n in the formula (I) is 10 to 10,000 and which does not impair the saturated polyester primary molded article. Water, methanol, acetone, dichloroethyl ether, methylene chloride and the like can be used. Further, among these, two or more kinds having compatibility can be mixed and used as a solvent.

The content of polyglycols in the solution must be 0.01 to 60% by weight, preferably 1 to 30% by weight. If the content is too small, it becomes difficult to form a protective film, and if it is too large, coating becomes difficult.

The coating solution according to the invention of claim 1 is applied to a primary molded product of a saturated polyester container and the solvent is removed by evaporation to form a protective film which is a film on the surface of the primary molded product. is there. This protective film covers the surface of the primary molded product and at the same time provides lubricity, and prevents the surface of the primary molded product from being scratched by the friction between the primary molded products or the friction between the primary molded product and the alignment guide. Play a role.

Since the above-mentioned protective film is a polyglycol having n in the formula (I) of 10 to 10,000, it is volatilized and removed when the primary molded product is reheated, and the saturated polyester container as a product is removed. Barely remains.

When the saturated polyester container to be molded is a bottle generally used as a beverage container, as shown in FIG. 1, the protective film 1 is formed so as to cover the entire area below the neck 3 of the primary molded product 2. However, it is preferable that a wide range can be protected. Further, since the neck portion 3 is generally not a portion stretched at the time of blow molding but is removed from the heating region at the time of reheating, in order to prevent the polyglycols from remaining, the neck portion 3 is removed from the formation region. It is preferable to remove it.

By the way, scratches on the surface of the primary molded product occur between the molding of the primary molded product and the reheating thereof.
In particular, it tends to occur at the time of alignment supply to the reheating step. Therefore,
It is necessary to form the protective film by coating and drying the coating liquid on the primary molded product before the alignment and supply to the reheating step. Further, in order to surely prevent the surface of the primary molded product from being scratched, it is preferable to form the protective film by coating and drying the coating liquid immediately after cooling the molding of the primary molded product.

The application of the coating liquid is most conveniently carried out by immersing the primary molded product in a container containing the coating liquid, but spray coating or brush coating can be used. Further, volatilization and removal of the solvent after coating may be carried out by natural drying, but it may also be carried out by forced drying accompanied by heating or blowing.

As the saturated polyester in the present invention, a thermoplastic polyester whose main repeating unit is ethylene terephthalate, that is, polyethylene terephthalate is preferable, and particularly ethylene terephthalate component is 7
0% by weight or more, I. V. A value of 0.5 or more is preferable. Further, additives such as a colorant, a heat deterioration preventing agent, an antioxidant, an ultraviolet absorber, an antistatic agent, an antibacterial agent and a lubricant may be appropriately added.

As the polyethylene terephthalate, a part of the terephthalic acid component is prepared by alicyclic dicarboxylic acid such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid or diphenyl sulfone dicarboxylic acid. Substituting one or more of other difunctional carboxylic acids such as adipic acid, sebacic acid, azelaic acid and other aliphatic dicarboxylic acids, P-β-hydroxyethoxybenzoic acid, ε-oxycaproic acid and other oxy acids. It may be a copolymer.

As the polyethylene terephthalate, a part of the ethylene glycol component is used, for example, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene glycol, diethylene glycol, 1,1-cyclohexanedimethylol, Copolymers substituted with one or more polyfunctional compounds of other glycols such as 1,4-cyclohexanedimethylol and 2,2 (4′-β-hydroxyethoxyphenyl) sulfonic acid and their functional derivatives. But it's okay.

[0022]

【Example】

Example 1 I.D. V. A primary molded product 2 as shown in FIG. 1 was obtained by injection molding using polyethylene terephthalate having a value of 0.7 (“RT543C” manufactured by Nippon Unipet Co., Ltd.).

Next, the portion below the neck 3 of the primary molded product 2 was immersed in a 10% by weight aqueous solution of polyethylene glycol (“Carbowax # 8000” manufactured by Union Carbide) for 30 seconds and taken out for 24 hours. After naturally drying to form the protective film 1, the film was randomly stored overnight in a plastic container.

The next day, the above-mentioned primary molded product 2 was transferred from the plastic container to an aligning machine, and then reheated and biaxially stretch blow molded to obtain a polyethylene terephthalate bottle (PET bottle).

The number of scratches on the surface of 12 PET bottles obtained as described above was visually inspected. The average number of scratches is shown in Table 1.

Further, there was almost no residual polyethylene glycol on the surface of the obtained PET bottle.

Comparative Example 1 The number of scratches was examined in the same manner as in Example 1 except that the aqueous solution of polyethylene glycol was not applied and dried. The average number of scratches is shown in Table 1.

[0028]

[Table 1]

[0029]

EFFECTS OF THE INVENTION The present invention is as described above, and at the time of manufacturing a saturated polyester container, the protective film can prevent the primary molded product from being scratched, and a high-quality saturated polyester container can be easily manufactured. Is what you get.
Further, since this protective film is volatilized when the primary molded product is reheated and does not remain in the product, there is no problem in hygiene.

[Brief description of drawings]

FIG. 1 is a front view of a primary molded product having a protective film formed by coating and drying a coating liquid according to the present invention.

[Explanation of symbols]

 1 Protective film 2 Primary molded product 3 Neck

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Claims (3)

[Claims] 1. HO— (R—O) _n —H (R is alkylene having 1 to 4 carbon atoms, and n is 10 to 100.
00 is an integer. ) The compound represented by
A coating solution for protecting a saturated polyester primary molded article, which is a solution containing 0% by weight. 2. On the surface, HO— (R—O) _n —H (R is alkylene having 1 to 4 carbon atoms, and n is 10).
It is an integer of 10000. ) A saturated polyester primary molded article with a protective film, which is formed with a coating film of the compound represented by the formula (1). 3. A biaxially stretched saturated polyester container, characterized in that the coating solution according to claim 1 is applied to the surface of a saturated polyester primary molded product to volatilize and remove the solvent before the aligned supply to the reheating step. Blow molding method.