JP3464531B2 - Deep drawn thermoformed polyester container - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deep drawn polyester container having good thermoformability, particularly improved transparency and uneven thickness of the container. 2. Description of the Related Art Saturated polyesters, especially crystalline polyester resins represented by polyethylene terephthalate (hereinafter abbreviated as PET), include fibers, sheets,
Widely used as a polymer for film, carbonated beverages, taking advantage of its excellent chemical resistance and low gas permeability,
It has also been applied to beverage bottles such as juice and beer, cosmetic containers, food trays, and the like. Among these, amorphous polyester sheets called A-PET have attracted attention because of their excellent recyclability, low pollution, and food safety. I have. This polyester sheet is used as a blister pack for food and medicine containers and miscellaneous goods by thermoforming,
Utilizing its excellent transparency, it is used as a clear case for cosmetics, electrical equipment, and the like. Conventionally, since such a saturated polyester sheet has crystallinity, if it is excessively heated at the time of thermoforming, it causes a whitening phenomenon due to crystallization and impairs the excellent transparency of A-PET. In particular, when thermoforming a cup-shaped deep drawing container or a container with complicated ribs, it is necessary to sufficiently heat the sheet during thermoforming to make it soft, and with unmodified polyester, the container becomes cloudy or uneven thickness. The problem is that the appropriate thermoforming condition width is very narrow, and improvement has been desired. There have been many proposals for improving the thermoformability of polyester sheets. For example, as described in JP-A-51-81857 and JP-A-51-38335, there is a method of copolymerizing a component that inhibits crystallinity and preventing crystallization during heating. However, in the method of copolymerizing a small amount of a component that inhibits crystallinity, the effect of improving thermoformability is low, and it is difficult to improve uneven thickness during deep drawing. Further, by increasing the amount of the copolymer component, the thermoformability is improved.
-The flexibility and impact resistance of PET are impaired, which is not preferable. The inventors of the present invention have made intensive studies to solve such conventional problems, and as a result, have found that at least one side of polyester having an intrinsic viscosity of 0.5 to 0.75 is used. A container obtained by deep drawing thermoforming a polyester sheet obtained by laminating a polyester sheet having an intrinsic viscosity of 0.5 to 0.90 obtained by copolymerizing 1,4-cyclohexanedimethanol in a specific range with A, -It has been found that the transparency and mechanical strength inherent in PET are maintained, the thickness is not uneven, and the economy is very excellent, and the present invention has been achieved. That is, the present invention relates to (A) a dicarboxylic acid component containing terephthalic acid as a main component, 0 to 90 mol% of ethylene glycol and 10 to 100 mol of 1,4-cyclohexanedimethanol. % Of a glycol component, and having an intrinsic viscosity of 0.60 to
A polyester laminate comprising: a layer made of a polyester having a viscosity of 0.90; and (B) a layer made of a polyester obtained by condensation polymerization of terephthalic acid and ethylene glycol and having an intrinsic viscosity of 0.5 to 0.75. A sheet wherein the intrinsic viscosity is (A)> (B), the (A) layer is laminated on at least one side, and the (A) layer is in the range of 1 to 30% of the total thickness of the sheet Is a polyester container obtained by deep drawing thermoforming with a drawing ratio of 0.8 or more. The polyester used for the main layer of the present invention is P
As well as ET, part of the terephthalic acid component is at least one other dicarboxylic acid component such as isophthalic acid, adipic acid, diphenylcarboxylic acid, diphenylether dicarboxylic acid, diphenylsulfone dicarboxylic acid, sebacic acid, naphthalenedicarboxylic acid, etc. And a copolymer in which part of the ethylene glycol component is replaced with at least one other glycol component such as diethylene glycol, hexamethylene glycol, trimethylene glycol, propylene glycol, cyclohexane dimethanol, neopentyl glycol, butylene glycol, etc. And polyester. [0010] The total proportion of the copolymer components in the copolymerized PET is preferably 10 mol% or less based on the total acid components. Further, it may contain a trifunctional or more functional compound or a monofunctional compound within a range considered to be substantially linear. Furthermore,
A heat stabilizer, a fluidity improver, an ultraviolet absorber, an antistatic agent, an antifogging agent and the like can be added to the polyester within a range that does not lower the transparency. When matting is required, a coloring agent such as titanium dioxide, calcium carbonate, iron oxide, or carbon black can be contained. The intrinsic viscosity at 20 ° C. is 60/40 by weight.
In a phenol / tetrachloroethane mixed solvent, the intrinsic viscosity needs to be 0.5 to 0.75, and particularly preferably 0.6 to 0.75. If it is less than 0.5, the mechanical strength of the container is not sufficient, and particularly the impact strength at low temperature is not sufficient. In addition, the sheet is drawn down during thermoforming, which tends to cause uneven thickness and wrinkles in the molded product, which is not preferable. On the other hand, when the intrinsic viscosity exceeds 0.75, it is necessary to carry out solid-state polymerization of the raw material PET resin, which is inferior in economical efficiency. Further, the copolymer polyester to be laminated on the surface of the present invention comprises a dicarboxylic acid component containing terephthalic acid as a main component, from 0 to 90 mol% of ethylene glycol and 10 to 100 mol% of 1,4-cyclohexanedimethanol. The amount of 1,4-cyclohexanedimethanol obtained by polycondensation of the resulting glycol component and copolymerized is preferably 25 to 35 mol%. If it is less than 10 mol%, the effect of improving the impact properties is small. The ratio of cis and trans of 1,4-cyclohexanedimethanol used is not particularly limited, but is 4: 6.
0 to 10 is good in terms of impact strength. The intrinsic viscosity needs to be 0.5 to 0.90, particularly preferably 0.6 to 0.90.
0 to 0.90. When the intrinsic viscosity is lower than 0.50, the mechanical strength of the final product is not sufficient, and particularly the impact strength at low temperature is not sufficient. Further, when the intrinsic viscosity of the surface layer is slightly higher than that of the main layer, a thermoformed product having good transparency with less occurrence of transfer marks and drag lines of plug assist in the thermoformed product can be obtained. Aperture ratio (ratio of container depth to container diameter)
When thermoforming a deep drawn thermoformed product or a complicated tray with a rib shape exceeding 0.8, it is necessary to soften the sheet sufficiently during heating, and the surface of the molded product is unmodified A-PET. Fogging. This is thought to be due to the fact that the oriented skin layer on the sheet surface at the time of sheet formation crystallizes during heating during thermoforming.Deep drawing is performed only by laminating a copolyester of a specific composition only on the very surface layer of the sheet. It was found that the properties and the fogging of the container were greatly improved. The proportion of the copolymerized polyester laminated on the surface of the sheet to the whole sheet is 1 to 30%.
From the viewpoint of economic efficiency and quality stability, 5 to 20% is preferable.
If it is less than 1%, it becomes difficult to make the skin layer uniform. On the other hand, if it exceeds 30%, not only is the effect of further improving thermoformability small, but also a large amount of expensive copolyester is used, which is not economically preferable. The sheet thickness used for producing the present invention is not particularly limited, but is usually 50 to 3000 μm.
Preferably it is 350 to 2000 μm. The sheet can be obtained by melt-extrusion using an ordinary polyester extruder such as a single-screw extruder or a twin-screw vent-type extruder, and cooling the molten resin with a cooling drum. The sheet is preferably quenched as much as possible to prevent a decrease in transparency due to crystallization. The crystallinity of the main layer is preferably 10% by weight or less (density of 1.348 g / cm ³ or less) and the sheet haze is preferably 5% or less. In order to obtain the present invention, a known co-extrusion apparatus having a feed block die, a multi-manifold die and the like can be used. Also, it can be manufactured by a known technique such as melt lamination and dry lamination,
Coextrusion is preferred from the quality of the sheet. As a film forming method, there are a method of sandwiching and cooling between metal rolls (touch roll method), an electrostatic application method, an air knife method and the like. The method is preferred. The in-line recycle is performed by in-line recycling, in which a lug portion produced when a sheet is cut into a predetermined width during film formation, and a skeleton portion obtained by punching a container after thermoforming are pulverized and returned as raw materials.
Although generally used in ET, in the present invention, it can be blended with the main layer within a range that does not extremely lower the intrinsic viscosity of the sheet. The product of the present invention can be manufactured by any method such as vacuum forming, compressed air forming, hot plate forming, plug assist forming, reverse draw forming, air slip forming, or a combination of these methods. No problem. According to the present invention, the characteristics inherent in A-PET, such as transparency, mechanical properties, and recyclability, are maintained, there is no uneven thickness and the economical efficiency is extremely excellent. Ideal for beverage cups, trays with complicated ribs, blister packs, etc. The present invention will be described in more detail with reference to the following examples, but it should not be construed that the invention is limited thereto.
In addition, each characteristic value was measured according to the following method. (1) Intrinsic Viscosity A phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40 was measured at a concentration of 1.0 g / dl at 20 ° C. (2) Haze of Container Using a haze meter NDH-20D manufactured by Nippon Denshoku Co., Ltd., the haze (haze value) of the container was measured by a method according to JIS-K-7105. (3) Thermoformability Containers having a diameter of 80 mm and a draw ratio were prepared using a vacuum forming machine with plug assist. A case where a complete container was made was rated as ○, a sample with perfect shaping but poor transparency was rated as △, and a sample with poor shaping or incomplete shaping was rated x. (4) Thermoforming conditions Width The sheet surface temperature at which thermoforming was completely completed was measured by a non-contact infrared radiation thermometer. The sheet having a thermoformable sheet surface temperature width of 15 ° C or more was rated as ○, the sheet with a temperature of 10 ° C or more and less than 15 ° C was rated as Δ, and the sheet with a temperature less than 10 ° C was rated as ×. (5) Drop strength of container 20 cups in a cup-shaped container having a diameter of 80 mm and a depth of 80 mm.
0 g of water was put in, the lid was closed (engagement lid), and dropped on a concrete surface from a height of 2.5 m for evaluation. A sample that did not crack at all was rated as O, a sample with a probability of breaking of 10% or less was rated as Δ, and a sample with a probability of breaking greater than 10% was rated X. Examples 1-2 and Comparative Examples 1-6 Melt extrusion was performed from a T-die using a multilayer extruder equipped with a twin screw vent at 285 ° C. and a degree of vacuum of 5 mmHg at the vent portion, and the product was manufactured by a touch roll method. Table 1 with film thickness of 800 μm
Was obtained. Next, the above sheet was preheated to a temperature equal to or higher than the glass transition temperature and equal to or lower than the melting point. A cup-shaped container was prepared and evaluated. Table 1 also shows the evaluation results. [Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B29L 22:00 B65D 1/00 B (56) References JP-A-5-162271 (JP, A) JP-A-5-212840 ( JP, A) JP-A-7-60924 (JP, A) JP-A-2-27639 (JP, A) JP-A-4-180958 (JP, A) JP-A-4-1355752 (JP, A) JP JP-A-5-329974 (JP, A) JP-A-7-323513 (JP, A) JP-A-7-108583 (JP, A) JP-A-8-1767 (JP, A) (58) .Cl. ⁷ , DB name) B32B 1/00-35/00 B29C 51/00-51/46

Claims (1)

(A) A dicarboxylic acid component containing terephthalic acid as a main component, ethylene glycol in an amount of 0 to 90 mol%, and 1,4-cyclohexanedimethanol in an amount of 10 to 1%.
The polycondensation with a glycol component consisting of 00 mol% is carried out,
And a layer intrinsic viscosity of the polyester is 0.60 to 0.90, (B) terephthalic acid and ethylene glycol caused to condensation polymerization, and intrinsic viscosity of the polyester is 0.5 to 0.75 the layer, from A polyester laminate constituted, wherein the intrinsic viscosity is (A)> (B), the (A) layer is laminated on at least one side, and the (A) layer has a thickness of 1% of the entire sheet. A polyester container obtained by deep-drawing thermoforming a sheet having a draw ratio of 0.8 to 30%.