JPS5836408A - Manufacture of polyester molded item - Google Patents

Abstract

PURPOSE:To obtain the titled molded item having high resistance to shock and heat, by heating a composite sheet consisting of a polyester layer and a polypropylene layer at specified temperatures, and deep drawing the sheet with the polyester layer being the innermost layer of the molded item. CONSTITUTION:A composite sheet consisting of a polyester (e.g. polyethylene terephthalate 80% of which consists of units of ethylene terephthalate, etc.) sheet layer A and a polypropylene sheet layer B is heated to 160-230 deg.C, and is deep drawn by vacuum molding to obtain the intended molded item with the innermost layer being the layer consisting of the constituent A. In the manufacture of the composite sheet, it is preferable to extrude the constituent B on the sheet of the constituent A to be coated therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a polyester molded product having high impact strength and heat resistance, and its purpose is to improve the impact resistance and heat resistance of a deep-drawn molded product made of Flea 4IK polynisdel. The purpose of the present invention is to provide a manufacturing method that improves properties.

Sheets of polyethylene terephthalate have traditionally been used as biaxially stretched films in electrical goods, printing fields, agricultural materials, and packaging fields. Cups and the like are beginning to be used in the food packaging field.

Although polyethylene terephthalate is a crystalline polymer, its crystallization rate is slower than that of polyethylene, polypropylene, polyamide, etc., and therefore an amorphous sheet can be obtained by rapidly cooling it from a molten state.

As a result, a highly transparent sheet can be obtained.

Furthermore, since polyethylene terephthalate is a crystalline polymer, when the stretch ratio exceeds about 2 times, the toughness increases with the stretch ratio due to the molecular orientation effect and the effect of promoting crystallization. As a result, compared to amorphous polymers such as polyvinyl chloride and polystyrene, the thickness of the molded product can be made more uniform when deep drawing is performed. Furthermore, when a non-quality transparent sheet is crystallized by stretching, the sheet does not turn white even if the degree of crystallinity is high.

For these reasons, thermoformed polyethylene terephthalate products are highly transparent and tough.

However, the side walls of the deep-drawn product made of polyethylene terephthalate are almost uniaxially elongated.

For this reason, there is no problem at all when using it for normal packaging purposes, but when using it under harsh conditions, for example 7
When a beverage is filled at a temperature close to 0° C. and a drop test is performed at a temperature below freezing, there is a drawback that some vertical cracks occur in the side wall portion.

As a result of intensive studies on a method for manufacturing a molded product free from such defects, the present invention has developed a composite sheet consisting of at least two layers, a polyester sheet layer and a polyester sheet layer, in a specific temperature range so that the innermost layer of the molded product becomes a polyester sheet layer. The present invention was achieved by discovering that a molded product free from the above-mentioned drawbacks can be obtained by deep drawing.

That is, the gist of the present invention is to heat a composite sheet consisting of at least two layers, a polyester sheet layer and a polypropylene sheet, to a temperature of 160 to 230°C [K], and deep-ply it so that the innermost layer of the molded product becomes the polyester sheet layer. A method for manufacturing polyester molded products that uses drawing and vacuum forming to eliminate mold.

The polynisdel used in carrying out the present invention is polyethylene terephthalate or ethylene terephthalate copolymer in which the number of repeating units is 80 or more ethylene terephthalate units, furthermore, polynisdel is 80 or more by weight of polyethylene terephthalate, and other thermoplastic resins are 20 weight-
It refers to a tree*S compound consisting of the following:

Other additives may be added to the polyester as necessary.

For example, it may contain an anti-quaking agent, a nucleating agent, and the like.

Further, the polypropylene used in carrying out the present invention refers to a polypropylene homopolymer, a random copolymer or a block copolymer with improved impact resistance.

The composite sheet used in the present invention is composed of at least two sheet layers of the above-mentioned polyester and polypropylene.

In the case of three or more layers, it is necessary that one of the outermost layers is composed of a polyester sheet layer.The above composite sheet may be manufactured by any method, but in general, polypropylene is added to a polyester sheet. Extrusion coating method is preferred. Ethylene-vinyl acetate emulsion adhesive to improve adhesion between polyester sheet and Volip WS Hiren sheet.

An ionomer or the like may be applied.

All conventional vacuum deep drawing techniques can be used to deep draw the composite sheet, but a vacuum forming method using a pre-stretching pressure 9 with a plug is preferred. 160-230 when the composite sheet is deep drawn and vacuum formed
It is necessary to heat and shape the product to a temperature of °C. When polyester is heated to a temperature in this range and deep drawn, it hardly causes any molecular orientation even if it is arc-stretched, so the tear strength of the resulting molded product becomes strong and the vertical cracking phenomenon described above can be suppressed. can. When molded by heating at a temperature of 160° C. without grooves, polynisdel molecules become oriented, and as a result, vertical cracks tend to occur in the side walls of the molded product. Moreover, it is not preferable to perform stable molding at a temperature exceeding 230°C.

In the present invention, deep drawing and vacuum forming must be carried out so that the innermost layer of the resulting molded product becomes the polyester sheet layer constituting the composite sheet. This is K
For example, even if the container is filled with various beverages, no problem arises because it is hygienic.

The present invention has the characteristic that it is possible to easily produce a deep-drawn product that does not cause vertical cracking when dropped at low temperatures, has excellent shape stability at high temperatures, and has high impact strength and high heat resistance.

The present invention will be specifically explained below based on the implementation example.

Note that the intrinsic viscosity of polyethylene terephthalate and polypropylene was measured by the following method.

Intrinsic viscosity of polyethylene terephthalate = 7 enol/
The polymer was dissolved in a mixed solvent of T-trachloroethane (50,150 weight ratio) and measured at 25°C.

Intrinsic viscosity of polypropylene: Measurement was carried out at 135°C using decalin as a solvent.

Example 1 A sheet of polyethylene terephthalate having an intrinsic viscosity of 0.73 and an intrinsic viscosity of 1.2 ml was placed between two layers of 4 0.2 ml thick sheets.
5-no polypropylene with a thickness of 0. VC to become I m
A composite sheet consisting of three 5'-layered layers was applied to a high-speed inline continuous vacuum forming machine with an own diameter of 70 m and a drawing ratio of 1.35.
A deep-drawn cup molded product was molded using 36 cavities. The sheet temperature before molding was 175°C.

After inserting and integrating the obtained deep-drawn cup molded product into a paper cup, 90% of the total volume was filled with 67°C hot water, immediately sealed with aluminum foil coated with heat-sensitive adhesive, and cooled to 3°C. did. After cooling, 100 pieces were dropped from a height of 150 cIL, and no damage occurred.

Comparative Example 1 A 0.5 m thick sheet made of polyethylene pre-7 tallate with a degree of When tested, the failure rate reached 85-.

Claims (1)

[Claims] A composite sheet consisting of at least two layers, a polyester sheet layer and a polyester sheet layer, is heated to a temperature of 160 to 230°C, and deep drawing vacuum forming is performed so that the innermost layer of the molded product becomes a polynisdel sheet layer. A method for manufacturing polyester molded products.