JPS62231720A - Polyester vessel and its manufacture - Google Patents

Abstract

PURPOSE:To mold efficiently a polyester vessel which possesses excellent heat resistance and favorable adhesion to a lid material, by a method wherein crystallinity of a thermally bonding part to the lid material in the vessel is less than a specific value and that of the bottom and/or the side of the vessel is more than the specific value. CONSTITUTION:The titled vessel provided with a thermally bonding part to bond to a lid material is obtained by molding a sheet made of polyester having polyethylene terephthalate for its main constitutent ingredient. Crystallinity of the thermal bonding part is less than 20% and that of the bottom and/or the side is more than 20%. The sheet made of the polyester is made to soften through heating in a state that the crystallinity of the same is less than 20% and the vessel made of the polyester is manufactured by applying thermoforming to the sheet by a mold which has been kept at the temperature falling within a range of the crystalline temperature of the polyester. At that time a cooling member which has been kept at the temperature falling within the temperature range of less than the glass transition temperature of the polyester +20 deg.C is brought into contact with the thermal bonding part to the lid material in the vessel.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a polyester container and a method for manufacturing the same. The present invention relates to a polyester container which can be easily heat-bonded with a lid material, and a method for manufacturing the same.

[Prior art]

Molded bodies obtained by thermoforming sheets made of polyester, particularly polyethylene terephthalate, are widely used as containers for foodstuffs, etc. In recent years, as described in JP-A-59-62660, for example, molded bodies have been widely used as containers for foods. Aged polyester molds with improved heat resistance and deformation +11 have come to be used as ovenable trays. The polyester container is typically prepared by thermoforming a polyethylene terephthalate sheet using a one-time high temperature mold in which the polyethylene terephthalate can crystallize.

However, the polyester containers obtained by this method have low thermal adhesion to ordinary lid materials because the polyester is crystallized, and in particular, they do not maintain adhesive strength even after hours of high-temperature treatment such as retort sterilization. Since it has the disadvantage of being difficult, its education is desired.

[Purpose of the invention]

The present invention was made to solve these problems, and its purpose is to efficiently mold a polyester container that has excellent heat resistance and good adhesion to the lid material, and 8 containers thereof. Our aim is to provide a method to do so.

[Structure of the invention]

As a result of intensive research into a polyester container and its molding method that do not have the drawbacks described above, the inventor has discovered that after heating a polyester sheet to a specific degree of crystallinity,
The present invention was achieved by discovering that the defects could be improved by thermoforming using a mold kept at a specific temperature.
That is, the present invention provides: (1) a container obtained by thermoforming a polyester sheet containing polyethylene terephthalate as a main component, wherein the degree of crystallinity of the part of the container that is thermally bonded to the lid material is 20%; (2) a polyester container characterized in that the degree of crystallinity of the bottom and/or sides of the container is not less than 20, and (2) a substantially amorphous container whose main constituent is polyethylene terephthalate; When producing a polyester container by heating and softening a polyester sheet with a crystallinity of less than 20% and then thermoforming it in a mold that is kept within the crystallization temperature range of the polyester, This is a method for producing a polyester container, which comprises bringing a cooling member, which is maintained at a temperature within the glass transition temperature of the polyester +20° C., into contact with the thermally bonded portion with the lid material.

To explain the present invention (1), polyethylene terephthalate in the present invention includes not only homopolymers thereof but also those in which a part of the terephthalic component or a part of the glycol component is replaced with another acid or glycol.

For example, part of the acid component is isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarbohydrate/acid.

Aromatic dicarboxylic acids such as diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, etc.; alicyclic dicarboxylic acids such as hexahydroterephthal 91 hequinahydroisophthal rR; adipic acid.

Aliphatic dicarboxylic acids such as cepacic acid, azillaic acid, etc.; other difunctional carboxylic acids such as oxyacids such as p-β-hydroxyethoxybenzoic acid, p-oxybenzoic acid, ε-oxycaproic acid, etc. Examples include those substituted with a component greater than or equal to IMi. Further, a part of the 1-functional ethylene glycol component may be added to, for example, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neoventerene glycol, diethylene glycol, 1.1-cyclohexane dimethylol, 1.4
-cyclohexane dimethylol, 2,2-bis(4-β
-hydroxyethoxyphenyl)propane, bis(4-
of other glycols such as β-hydroxyethoxyphenyl) sulfone! Copolyesters substituted with the above components are also included. The copolymerization component CI Nm W1 of these copolyesters A is preferably 3 molar or less based on the total acid components. Among these, a homopolymer of polyethylene terephthalate is preferred.

The polyester sheet used in the present invention is a substantially amorphous sheet mainly composed of polyethylene terephthalate, and preferably has an intrinsic viscosity of 0.8 or more. The polyester sheet may contain additives or mold release II that have the effect of promoting crystallization, and
It may also be a sheet in which polyethylene (hereinafter sometimes referred to as PE) and polypropylene (hereinafter sometimes referred to as PP) are mixed in an amount of 1 to 30% by weight. This polyester sheet uses PET having a crystallinity of less than 20 inches, and the crystallinity here is a numerical value determined by formulas (11 to (31).

ρo = 1.333- (Wx 0.0040)-
--”...(1) ρc=1.455-(WXo, 005
3)--=-... f2) C=((ρ-ρ0)/(ρ
C-ρo) l
If the crystallinity of 1P1uT is 20% or more, the shapeability during thermoforming will be poor, and the thermal adhesion to the lid material will be poor.

In the present invention (2), the polyester sheet has a crystallinity of 2
The sheet is softened and thermoformed in a state of less than 0%, but in order to maintain the crystallinity in this state, it is preferable to heat the sheet to a surface temperature of 140° C. or higher within 15 seconds. If the above-mentioned time is exceeded, the crystallization induction period of PET is passed, and a phenomenon occurs in which the PET portion in the sheet rapidly crystallizes, resulting in poor shaping properties, which is not preferable.

Furthermore, in the present invention, the mold temperature is set within the crystallization temperature range of polyester, that is, using a differential calorimetry needle (DSc), and the sample is
When the temperature is raised and lowered at a rate of ℃/-, the polyester is heated by a mold that is maintained at a temperature higher than the crystallization initiation temperature (ToI) and lower than the crystallization initiation temperature (T'co) when the temperature is lowered. A polyester container is manufactured by molding, and at this time, the glass transition temperature (TV) of the polyester is in the fm degree range below +20°C (particularly preferably below Tf) at the thermally bonded part with the lid material of the container. This requires a step of bringing the cooling member into contact with the cooling member.

If the temperature of this cooling member is higher than Tt+20℃
When the temperature is K, the mold release between one member and the container becomes difficult, especially when the temperature is T. I
When the temperature is higher than that, the crystallinity of the container increases, so
The effect of the present invention is impaired.

Furthermore, if the mold temperature is out of the crystallization temperature range of the polyester, the crystallinity of the bottom and/or side portions of the container may be insufficient and the heat resistance of the container may not be improved, or the container may shrink immediately after thermoforming. becomes larger.

By the thermoforming method described above, the degree of crystallinity of the thermally bonded part with the lid of the container is less than 20 inches, preferably less than 10 degrees, and the crystallization If of the bottom and/or side part of this container is 2.
A polyester container with a coefficient of 0 or more, preferably 30 or more is obtained.

In the present invention, such polyester sheets are thermoformed under specific conditions to obtain containers with excellent heat resistance and heat adhesive properties in the shape of trays, cups, etc. Press the sheet against the desired mold, eliminate the air in the gap between the mold and the material, and press the sheet into close contact with the mold under atmospheric pressure (vacuum forming), or pressurize the sheet with compressed air above atmospheric pressure and press it against the mold. A general term for molding that uses both vacuum and compressed air.

〔Effect of the invention〕

The polyester molded article obtained by the thermoforming method of the present invention has a desired shape and dimensions, has excellent heat deformation resistance and thermal adhesion to a lid material, and can be advantageously used as an ovenable tray or the like.

〔Example〕

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

The measurement conditions for the main physical property values and the molding value standard are as follows.

(1) η14r viscosity x [IV]: Measured at 35°C in 0-chlorophenol or phenol/tetrachloroethane mixed vinegar medium.

(2) Density [ρ]: Measured at 25°C in a density gradient tube made of carbon tetrachloride and n-hebutane.

(3) Glass transition temperature J1]: Differential heat #:, meter (Seiko Electronics Co., Ltd. "11! ID S C-20r
Measured at a heating rate of 20°C/sea bream using the method).

(4) Temperature at which temperature increases during crystallization (Ta process): Measured under the same conditions as Tr.

(5) Melting point (polyester) ('rmE):
Measured under the same conditions as Ty.

(6) Crystallization onset temperature upon cooling [ToD]: differential pA
The temple was held at 290℃ for 3 minutes at 20℃.
/Measured by the rate of temperature drop in agony.

(7) Melting point (Boriolephiy) (Tmo):
Measured under the same conditions as TCD.

(8) Tensile @impact strength (Ia): Tester Sangyo Co., Ltd. Fil Tongile Impact Ta5
Measured at ter.

(9) Heat Shrinkage Resistance C3v): ) The capacity of the lay-type container was heat treated at 230°C for 10 minutes.
Fixed.

θI Mold release property: Evaluated in a state where the shape is collapsed when the molded product is pressed into the mold (4).

Oυ Moldability: Evaluate the mold traceability or shape defects of the molded product that has been submerged by thermoforming.

QX5 Heat/- Greasy: The material sealing part and the lid material were thermally bonded to the cover of the container with a width of 15IIJ using a heat sealer "K" and the adhesive strength was measured using a tensile tester.

T-45 type heat sealer 0 made by Toyo Tester Kagari (USA) Heat sterilization resistance: After processing the heat-sealed sample at 120°C for 30 minutes in a moist heat sterilization processing bag @lf='N (retortable), the adhesive strength was evaluated. Measured using a tensile tester.

Silk Yamato Scientific MSM-21 type autoclave The heat sealability evaluation was based on adhesive strength of 1 odor/15
+am or more: ○ (good) 0.3-1 shame/15u
In the case of: Δ (slightly good) 0, 3 In the case of K9/15 mm or less: × (poor).

Further, retortability was evaluated in the same manner as the evaluation of heat sealability.

However, containers with large deformation were also rated as × (defective).

Examples 1 to 6, Comparative Examples 1 to 5, and Reference Example I V 1.
After blending 100 parts of dry chips obtained by drying No. 08 polyethylene tere-7 tallate (hereinafter abbreviated as PET) with hot air at 160°C for 5 hours and 0.4 part of talc, a die for sheet extrusion was attached to the tip. The mixture was fed into an extruder with a 30 rtal screw diameter. The mixture was melt-kneaded at an extruder cylinder temperature of 240 to 280°C, and the extruded sheet was cooled with a cooling roll to obtain a polyester sheet with a thickness of 0.5 Iu.

The polyester sheet has a melting point (TmFJ) of 7278°C.
250℃, TCI 135℃, TcD 190℃, ρ0
It was 1.338 f/i (crystallinity 4%) and IVo 93.

The sheet was put into a FC-IAPA-W type compressed air/vacuum forming machine manufactured by Asano Research Institute as a mold into a concave tray with an electric heater inserted and an engraved shape, height 135 mm, Wi 58U, depth 181 g. The mold is made by running cooling water inside as a cooling member. Vertical 140U, horizontal 65 ram
+Thickness 40. Vacuum forming was performed using a flat plate mold under the conditions shown in Table 1. Table 1 shows the density measurement values and moldability/molded body evaluation results.

The cooling member was brought into contact with the sealing portion of the container immediately after the sheet was placed in the mold and forming was started.

The outline is shown in Fig. 1 and Fig. 2.

In addition, for the lid material, a sheet with a wall thickness of 100 μm was used 3.3 times
P that was biaxially stretched at a magnification of 3 times and then heat-set at 200°C.
40% of isophthalic acid as an acid component on one side of the ET film.
I'ET (melting point: 157° C.), which was copolymerized with 12 moles of diethylene glycol as a glycol component, was coated with a thickness of about 15 μm.

As is clear from Table 1, in the case of comparison rows 4 and 5 and reference 11, in which the mold u m: is outside the crystallization temperature range of PBT, even if the heat sealability is good, the moldability or container The heat resistance is poor, and even if the mold temperature is within the crystallization temperature range of PET, cooling by the conventional method as in Comparative Example-1 or cooling by the cooling member as in Comparative Example-2 and 3 is insufficient. In this case, the side heat resistance of the container is good, but the heat sealability is poor.

In the present invention of Examples 1 to 6, resistance to 7A +
%, heat sealability, and retortability, and those of Examples 1 to 3 and 6 are particularly excellent.

Example 7.8 and Comparative Example 6 Example 1 except that 3 parts by weight of linear low density polyethylene with a melt index of 1.3 was added and no talc was added.
The mixture was fed to an extruder in the same manner as above to obtain a polyester sheet with a wall thickness of about 0.6 u.

The polyester sheet has a Tf of 74°C and a TmE of 249.
'C, Tm0101℃, TCI 135℃, Tco
182'C, ,11101,327f/ad (crystallinity 5%).

The sheet was vacuum formed in the same manner as in Example 1 under the conditions shown in Table 2.

Table 2 shows the density measurement values, moldability, and molded body evaluation results.

The material of the present invention had good heat resistance and heat resistance.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing how the container is molded in the present invention, and FIG. 2 is a sectional view showing the container separated from the mold and the cooling member after molding. In the drawings, 1 is a polyester container, 2 is a vacuum or pressure molding mold, 3 is a cooling member, 4 is a bottom of the container, 5 is a side of the container, and 6 is a lid material for the container that is in a low crystallization state. 7 is a part of the vacuum or plastic hole of the mold, 8 is a part of the compressed air introduction hole or vent hole of the cooling member, 9 is the adhesion of the cooling member to the container. The parts are shown respectively.

Claims (3)

[Claims] (1) A container equipped with a heat-bonded part for heat-bonding it to a lid material, which is obtained by molding a polyester sheet containing polyethylene terephthalate as a main component, and the heat-bonded part is crystallized. A polyester container, characterized in that the degree of crystallinity of the bottom and/or side portion of the container is 20% or more. (2) A polyester sheet containing polyethylene terephthalate as a main component is heat-plasticized with a degree of crystallinity of less than 20%, and then thermoformed into a container using a mold maintained within the crystallization temperature range of the polyester. 1. A method for producing a polyester container, which comprises bringing a thermally bonded portion of the container to a lid material into contact with a cooling member to suppress crystallization of the thermally bonded portion. (3) The method for producing a polyester container according to claim 2, wherein the temperature of the cooling member is within a temperature range of 20° C. higher than the glass transition point of the polyester.