JPH0246459B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to blow molded containers.
Specifically, the present invention relates to a blow-molded container with high adhesive strength at the pinch-off portion and good color tone. BACKGROUND ART In recent years, single-layer or multi-layer blow-molded containers having a polyamide layer as an inner layer have been used in a wide variety of applications. In blow-molded containers, the pinch-off part is easily destroyed or peeled off, so it is an important issue to improve the adhesive strength of the pinch-off part. A structure composed of a polyamide layer has been proposed (Japanese Patent Publication No. 57-2579). However, blow-molded containers made of polyamide containing copper halide, when used with copper halide in an amount sufficient to provide sufficient pinch-off bond strength, take on a brown to blue tone, especially copper iodide. When dried, the color is brownish, but when it comes into contact with water or alcohol, the color changes to blueish, making it unsatisfactory as a container. Furthermore, if the raw material polyamide is colored, even if dyes and pigments are used to color it, the color will be dull and it will be difficult to obtain a product with a bright tone. The inventors of the present invention have conducted extensive research in order to obtain a blow-molded container with excellent adhesive strength at the pinch-off part and a good color tone. As a result, the inventors have found that when polyamide containing a specific compound is used, a sufficiently satisfactory effect is obtained. The present invention was completed by learning that it is possible to do this. That is, the present invention aims to provide a blow-molded container of great industrial value, and its gist is that hypophosphorous acid, phosphorous acid, or an alkali metal or alkaline earth metal salt of phosphoric acid is This is a blow-molded container with excellent adhesive strength at the pinch-off portion of a single layer or a multilayer comprising the polyamide layer as an inner layer. The present invention will be explained in detail below. The polyamide used in the polyamide layer of the present invention includes lactams such as ε-caprolactam,
Polymers such as ε-amino acids such as aminocaproic acid, diamines such as hexamethylene diamine, nonamethylene diamine, metaxylylene diamine, and adipic acid, sebacic acid, dodecanedicarboxylic acid, terephthalic acid, isophthalic acid, and cyclohexanedicarboxylic acid. Examples include polymers obtained by polycondensing dicarboxylic acids such as nylon 6, 11, 12, 6.6, and nylon 6.6.
Examples include 6.10, 6T, 6/6.6, 6/6T, etc. These polyamides may be used in combination, and other resins such as ethylene/vinyl acetate copolymer, ethylene/acrylic ester copolymer, ionomer resin, etc. may be used as long as the gas barrier properties of the polyamide layer are not impaired. α to ethylene polymer,
A polyolefin resin with improved adhesion such as a modified ethylene copolymer obtained by graft polymerization of β-unsaturated carboxylic acid or the like may be blended. The hypophosphites, phosphites or phosphates used in the present invention include hypophosphites, phosphorous acids of alkali metals such as sodium and potassium or alkaline earth metals such as calcium, magnesium and barium. Examples include salts, acidic phosphites, phosphates, acidic phosphates, pyrophosphates, polyphosphates, etc., and it is particularly preferable to use sodium hypophosphite, potassium hypophosphite, etc. The content of the hypophosphite, phosphite or phosphate is about 0.01 to 5% by weight, preferably about 0.05 to 1% by weight, based on the polyamide layer. If it is too small, the effects of the present invention cannot be expected. On the other hand, if the amount is too large, the molecular weight of the polyamide decreases during molding, resulting in a decrease in viscosity, making blow molding difficult, or reducing the strength of the product, which is undesirable. Further, as a method for incorporating the hypophosphite, phosphite, or phosphate into the polyamide, a method such as dry blending or kneading the dry blend using an extruder or the like can be adopted. At this time, it is preferable to include a lubricant such as stearic acid, calcium stearate, magnesium stearate, ethylene bisstearamide, waxes, urea derivatives, etc., since this facilitates the mixing operation. The amount of lubricant used is 5% by weight or less based on the above hypophosphite, phosphite or phosphate;
The content is preferably about 1 to 4% by weight. If the amount is too large, the adhesive strength between the polyamide and other resins will be reduced in the case of multilayer blow molding. A spreading agent such as polyethylene glycol or its derivatives, mineral oil, silicone oil may also be used to uniformly blend the additives. The blow molded container of the present invention is molded using a single layer blow molding machine or a multilayer blow molding machine according to a known conventional method. In multilayer blow molded containers, the resin layer that forms the container together with the polyamide layer includes polyethylene, polypropylene, ethylene/vinyl acetate copolymer, etc., and is used for adhesion between these resin layers and the polyamide layer. Examples of the adhesive layer resin include the adhesive polyolefin resin described above. The blow-molded container of the present invention has greatly improved adhesive strength at the pinch-off portion, so it can be suitably used for everything from large containers such as gasoline tanks to small containers such as food and cosmetic containers. . In addition, since the color tone is good, the appearance of the contents is not impaired, and it is suitable as a colored container. EXAMPLES The present invention will be specifically explained below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, the adhesive strength of the pinch-off part was determined by filling a test container with water and setting the pinch-off part as the bottom surface with a diameter of 20 mm.
The sample was dropped from a height of 1 m so that the pinch-off part hit the steel ball, and the number of broken containers out of 10 test containers was expressed as ``pieces/out of 10''. In addition, the color tone was measured by cutting out the body of the sample container one week after filling with water and measuring the a value using a color difference meter (digital colorimeter AUD-CH2 model manufactured by Suga Test Instruments Co., Ltd.). and b value. A large negative value of a value indicates that green color has been present, and a large positive value of b value indicates that yellow color has been present. Examples 1 to 5 and Comparative Examples 1 to 2 Nylon 6 with a relative viscosity of 5.2 (manufactured by Mitsubishi Chemical Industries, Ltd.)
Hypophosphite, phosphite, or phosphate shown in Table 1 below is dry-blended with the pellets of NOBAMITSUDO 1040 (registered trademark), and this is then processed using a single-layer blow molding machine (manufactured by Japan Steel Works, Ltd., NB3B-). The parison was extruded using a machine (Model S50) at a resin temperature of 260°C and an extrusion rate of 20 kg/hr. This parison was placed in a mold and air blown to form a container with a thickness of 1 mm and an internal volume of 500 ml. The adhesive strength and color tone of the pinch-off portion of this container were as shown in Table 1 below. For comparison, the results when no additive was added and when copper iodide was added are also shown.

[Table] Example 6 Outer layer is high-density polyethylene (Mitsubishi Chemical Industries, Ltd.)
(Mitsubishi Chemical Corporation, registered trademark, Novatec BT-002), the intermediate layer is a modified ethylene copolymer made by graft polymerizing maleic anhydride to low-density polyethylene (Mitsubishi Chemical Corporation).
Co., Ltd. (registered trademark, Novatec PA220L), the inner layer of which is the same nylon 6 used in Example 1 and a dry blend of 0.2% by weight of sodium hypophosphite. (manufactured by) and blow molded the outer layer/middle layer/inner layer = 500μ/
A 500ml three-layer container of 50μ/100μ was manufactured. The adhesive strength of the pinch-off part of this three-layer container is 0.
out of 10, the a value was -1.34 and the b value was 3.02.

Claims (1)

[Scope of Claims] 1. Adhesive strength of a pinch-off portion of a single layer or a multilayer composed of a polyamide layer containing hypophosphorous acid, phosphorous acid, or an alkali metal or alkaline earth metal salt of phosphoric acid or a multilayer having the polyamide layer as an inner layer. Excellent blow molded container. 2. The blow-molded container according to claim 1, wherein the content of hypophosphorous acid, phosphorous acid, or an alkali metal or alkaline earth metal salt of phosphoric acid is 0.01 to 5% by weight based on the polyamide layer.