JPH02127437A - Sheet comprising polyester resin composition and hot-molded material thereof - Google Patents

Abstract

PURPOSE:To obtain the title film useful as containers for foods and drinks to be packed at high temperature, moldable into hot-molded materials having excellent heat resistance and impact resistance by blending a specific polyester and polypropylene in a specific ratio. CONSTITUTION:(A) 100 pts.wt. polyester having ethylene terephthalate as a main repeating unit is blended with (B) 1-30 pts.wt. polypropylene copolymerized with ethylene and maleic anhydride to give the aimed film or sheet. Further, the blend is preferably mixed with (C) 0.1-2 pts.wt. based on 100 pts.wt. of a crystal nucleating agent such as graphite or carbon black and further (D) an additive such as colorant.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a polyester film or sheet (hereinafter also simply referred to as a sheet) and a thermoformed product thereof, and more particularly, to a heat-resistant polyester film or sheet (hereinafter sometimes simply referred to as a sheet) and a thermoformed product thereof, and more specifically, for example, The present invention relates to a polyester film or sheet that can be efficiently molded into a container with excellent deformability and impact resistance, and a thermoformed product thereof.

[Prior Art] Films or sheets made of polyester, particularly polyethylene terephthalate, can be formed into trays or cups by thermoforming, and are widely used as raw materials for various containers. In particular, polyethylene terephthalate (hereinafter referred to as PE) is a polyolefin resin added to polyester.
PE film or sheet (sometimes abbreviated as T)
Molded products (thermoformed products) thermoformed under conditions that allow T to crystallize have excellent heat resistance, as described in JP-A-59-62660, and can be processed for food in ovens and microwaves. It can be used as a heat-resistant container such as an ovenable tray. However, PET containers obtained by the darning technique have the drawback of extremely poor mechanical properties, particularly impact resistance when handled at low temperatures, and an improvement has been desired.

[Objective of the Invention] The present invention has been made against the background of the above, and is an object of the present invention to mold a container that has excellent heat resistance and has excellent impact resistance even when used in sub-zero temperature conditions. The goal lies in the development of materials that work well. Moreover, it is important to develop a film or sheet that can be molded under favorable thermoforming conditions during molding.

Therefore, an object of the present invention is to provide a polyester film or sheet having excellent hygiene properties, and a thermoformed article obtained from the polyester film or sheet.

[Structure of the Invention] As a result of intensive research on polyester films or sheets and thermoformed products thereof, the present inventor has developed a method using a resin composition in which a specific polyolefin resin and a crystal nucleating agent are melt-mixed with polyester in a specific ratio. It has been found that the above-mentioned drawbacks can be overcome with a polyester film or sheet made of polyester, and a thermoformed article obtained by thermoforming this polyester film or sheet.

Furthermore, a layer consisting of a polyester composition obtained by melt-mixing a specific polyolefin resin, a crystal nucleating agent, and a coloring agent if necessary in a specific ratio; The above-mentioned also applies to multilayer films or sheets composed of two or more multilayers in which layers of polyesters of different compositions are blended in different proportions, and thermoformed products obtained by thermoforming the films and sheets. The inventors have discovered that the drawbacks can be improved and have arrived at the present invention.

That is, the present invention is comprised of the following items.

(1) From a resin composition (I) prepared by mixing 100 parts by weight of polyester (A) having ethylene terephthalate as a repeating unit and 1 to 30 parts by weight of polypropylene (B) copolymerized with ethylene and maleic anhydride. (2) A crystal nucleating agent (C) is added to the resin composition (I) according to claim 1, and a polyester (A) is added to the resin composition (I) according to claim 1.
A film or sheet made of resin composition (II) containing 0.1 to 2 parts by weight per 100 parts by weight,
(Here, crystal nucleating agents include graphite, carbon black, magnesium oxide, calcium silicate, magnesium silicate, talc, and kaolin.

Calcium carbonate, magnesium carbonate, sodium carbonate,
Potassium carbonate, zinc oxide, alumina.

Refers to at least one selected from the group of barium sulfate and calcium sulfate. ) (3) A film made of a resin composition (■) obtained by adding an additive (D) such as a coloring agent to the resin composition (1) or resin composition (n) according to claim 1 or 2; Sheet, (4) polyester (8), copolymerized polypropylene (B
), a multilayer film or sheet formed by laminating at least two layers of resin compositions having different mixing ratios of crystal nucleating agents (C) and additives (D), (5) any one of claims 1 to 4; A thermoformed article obtained by thermoforming the single-layer or multilayer film or sheet described in .

The present invention will be explained.

In the present invention, polyester includes not only a homopolymer of polyethylene terephthalate, but also a part of terephthalic brewing components such as isophthalic acid, naphthalene dicarboxylic acid, and diphenyl dicarboxylic acid.

Aromatic dicarboxylic acids such as diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, etc.Alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, etc.:
Aliphatic dicarboxylic acids such as adivic acid, cepatic acid, azelaic acid, etc.; p-β-hydroxyethoxybenzoic acid,
with one or more components of other difunctional carboxylic acids such as oxyacids such as ρ-oxybenzoic acid, ε-oxycaproic acid, etc., and/or a portion of the ethylene glycol component, such as trimethylene glycol, tetramethylene glycol. , hexamethylene glycol, decamethylene glycol, neopentyl glycol.

Diethylene glycol, 1,1-cyclohexane dimethylol, 1,4-cyclohexane dimethylol.

2.2-bis(4-β-hydroxyethoxyphenyl)
Includes copolyesters substituted with one or more components of other glycols such as propane, bis(4-β-hydroxyethoxyphenyl)sulfone, and the like.

The total proportion of copolymerized components in the copolyester is preferably 3 mol % or less based on the acetic acid component.

Among these, a homopolymer of polyethylene terephthalate is preferred.

In the present invention, polypropylene (hereinafter referred to as Co-P
1 to 30 parts by weight of (sometimes abbreviated as P) is melted. If the mixing ratio is lower than 1 part by weight, the effect of improving the toughness of the thermoformed product at low temperatures will be low, and if it is higher than 30 parts by weight, the toughness improving effect will be poor and the thickness distribution will be poor. This is not preferred because it is difficult to obtain a thermoformed product and the heat deformation resistance of the thermoformed product becomes poor. Co-PP
A particularly preferred mixing ratio is 5 to 15 parts by weight per 100 parts by weight of polyester.

The copolymerization ratio of the Co-pp is 5 to 30 mol% of ethylene, 0.5 to 5 mol% of anhydrous maleic, a Vicat softening point of 70 to 85°C, and a density of 0.88 to 85°C.
0.92 MCm3, melt flow rate (hereinafter referred to as MF)
(sometimes abbreviated as R) 4 to 8 are extremely finely dispersed in polyester and have a large effect of improving toughness.

The polyester film or sheet used in the present invention is
The Co-p containing polyethylene terephthalate as the main component
It is preferable that the substantially polyester component containing p and the crystal nucleating agent is amorphous, and that the polyethylene terephthalate constituting the film or sheet has an intrinsic viscosity of 0.65 or more.

If the intrinsic viscosity (sometimes abbreviated as IV) is lower than 0.65, it is not preferable because the impact strength of the thermoformed product decreases.

The crystal nucleating agent mixed in the present invention is graphite.

Carbon black, magnesium oxide, calcium silicate, magnesium silicate, talc, kaolin.

Calcium carbonate, magnesium carbonate, carbonic acid, sodium, potassium carbonate, zinc oxide, alumina,! It is an inorganic substance such as barium acetate and calcium sulfate, and is melt-mixed in an amount of 0.1 to 2 parts by weight per 100 parts by weight of polyethylene terephthalate. The preferred mixing ratio of the crystal nucleating agent is 0.3 to 1.0 parts by weight, and the mixing ratio is 0.1 parts by weight.
When the amount is less than 1 part by weight, the effect of the crystal nucleating agent is small, and it takes a long time to preheat the film or sheet when forming a thermoformed product, which is not preferable from the viewpoint of productivity. Moreover, if the amount is more than 2 parts by weight, the crystal nucleating agent will precipitate in the form of foreign matter on the film or sheet extruded by an extruder, impairing the appearance of the sheet, which is not preferable.

The density of the film or sheet of the present invention before thermoforming is preferably such that the density of the polyester component is 1.36 g/Cm3 or less, and the film or sheet is substantially amorphous and has a tensile impact resistance. Strength is 60Kg・Cm
/Cm2 or more. If the film or sheet is crystallized, the shapeability of the molded product will be poor when producing the molded product by thermoforming, and the tensile impact strength will be 60%.
If it is lower than Kg·C11l/Cm2, it is not preferable because the impact strength of the thermoformed product becomes low. Such an amorphous polyester film or sheet can be obtained by melt-mixing the composition of the present invention using an extruder, extruding it from a slit-shaped die, and rapidly cooling it using a cooling drum.

In addition, the degree of melt crosstalk between PET and Co-pp is
-PP It is preferable to knead well and homogenize so that the dispersed particle size of P is 10 μm or less.

Examples of means for finely dispersing Co-PP include, for example, preparing high-concentration Co-pp pellets in advance using an extruder and using them as master pellets during sheet production, a twin-screw extruder, or a single-screw extruder with a high compression ratio. It is effective to manufacture sheets using

Furthermore, when the multilayer film or sheet of the present invention consisting of two or more layers is discharged from a slit-shaped die, two or three or more kneading (melt mixing) means for melt-mixing the composition of the present invention are used to melt and mix the composition. 2 units (20
) It can be produced by discharging it from the above multilayer die and rapidly cooling it with a cooling drum.

The multilayer film or sheet is made of polyester (A),
C0-PP (B), crystal nucleating agent (C) and coloring agent (D
) can be made by laminating compositions with different compositions by changing the blending ratio. For example, in a resin composition (n) consisting of polyethylene terephthalate, Co-PP, and a crystal nucleating agent, one containing a small amount of talc as a crystallization nucleating agent and one containing barium sulfate may be laminated to form a 2@ sheet. Can be done. Of course, it is also possible to use the same crystal nucleating agent and change the blending values to produce Sea 1 to laminates made of two types of resin compositions.

The thermoformed article of the present invention is a molded article obtained by thermoforming the above polyester film or sheet.

Thermoforming in the present invention refers to vacuum forming in which a film or sheet is softened by heating and pressed against a desired mold, air in the gap between the mold and the material is excluded, and the film or sheet is brought into close contact with the mold under atmospheric pressure. A general term for compressed air forming in which a film or sheet is brought into close contact with a mold using compressed air at a pressure higher than atmospheric pressure, and forming that uses a combination of vacuum and compressed air.

The thermoformed product of the present invention has a low-temperature impact strength of 80 cm or more in a drop impact test and has excellent toughness, but it is necessary to further improve heat-resistant dimensional stability (also referred to as heat resistance). , obtained by heating the polyester film or sheet of the present invention to a moldable temperature and then molding it by keeping the mold temperature at or above the glass transition temperature of PET (hereinafter sometimes abbreviated as Tc). . The higher the mold temperature is, the better the heat resistance will be, but if it is too high, the toughness will decrease, which is not preferable. Although the upper limit of the mold temperature varies depending on the blending ratio of Co-pp, it is preferably in a range where the low-temperature impact strength is 80 cm or more, for example, 130° C. or less.

In addition, a coloring agent may be used within a range that does not impair the purpose of the present invention.

Inorganic fillers, barrier property-improving polymers, ultraviolet absorbers, or stabilizers for improving heat-resistant melt stability may also be included.

[Effects of the Invention] The polyester film or sheet of the present invention can be formed into a thermoformed product with excellent heat resistance and impact resistance, and the thermoformed product can be advantageously used as a container for foods such as curry.

[Example code] The present invention will be explained in detail with reference to Examples below.

The measurement conditions for the main physical property values are as follows.

(1) Intrinsic viscosity [IV]: Measured at 35°C using a solution from which insoluble matter was removed in a ○-chlorophenol or phenol/tetrachloroethane mixed solvent.

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

(3) Glass transition temperature fTg]: Differential calorimeter (DSC-20 manufactured by Seiko Electronics Co., Ltd.)
Measured at a heating rate of 20°C/min.

(4) Temperature-rising crystallization peak temperature [TCI]: Measured under the same conditions as Dingq.

(5) @ point (polyester > [TmE] :T(]
Measured under similar conditions.

(6) Crystallization peak temperature during temperature cooling [TCD]; A sample held at 290°C for 3 minutes using a differential calorimeter was
Measured at a cooling rate of min.

(7) Melting point (polyolefin >[Tmo]; TC
Measured under the same conditions as D.

(B) Thermal shrinkage rate [SH] Calculated using the following formula from the tray volume VH when a tray with an internal volume VO is filled with hot water at a predetermined temperature and then cooled to room temperature o -VH 3H = X100 [%] V.

(9) Tensile impact strength [Til: The strength of a dumbbell struck from a sample was measured at 20'C using a tensile impact tester manufactured by Tester Sangyo ■.

(10) Low-temperature impact strength After filling the Nidoray with water and heat-sealing it to the lid material, cool it in a new Hitachi manufactured EC-800HH-1 refrigerator-freezer until the temperature reaches -20℃. The tray was dropped onto a concrete floor with its bottom facing downward, and the critical fall height at which the tray would not break was determined.

(11) Formability: A tray-shaped mold was attached to the FC-IAPA-W vacuum-pressure forming machine manufactured by Asano Laboratory, and the separation was performed when vacuum forming was performed at a predetermined mold temperature with various sheet heating conditions. Characteristics such as moldability, sheet sag, and mold traceability are evaluated.

(12) Heat resistant temperature [°C]; Upper limit of hot water temperature at which the hot water shrinkage rate of the tray is within 5%.

Examples 1 to 7 and Comparative Examples 1 to 2 PET pellets with an intrinsic viscosity of 0.81 were dried at 160°C for 5 hours to obtain dry pellets with a moisture content of about 0.005 wt%.

These dried PET pellets were blended with Co-P P and a crystal nucleating agent in the proportions shown in Table 1 to obtain various compositions, and these were each mixed with a 40 mm screw diameter equipped with a die for sheet extrusion at the tip. It was fed into the extruder. The mixture was melt-kneaded at an extruder cylinder temperature setting of 240 to 280'C, and the extruded sheet was cooled with a cooling roll to obtain polyester sheets of various compositions with a wall thickness of 0.3 mm.

Table 1 shows the density of each sheet.

These sheets were engraved as a mold into a FC-IAPA-W type vacuum-pressure forming machine manufactured by Asano Laboratory, with a length of 135 mm.
, a concave tray type with a width of 58 mm and a depth of 18 mm was installed,
Vacuum forming was carried out under the conditions that the mold temperature was maintained at 80° C. and the forming time was 5 seconds. The heat resistance, impact resistance, and moldability of the thus obtained tray were evaluated. The evaluation results are shown in Table-1.
As is clear from the results in Table 1, the sheet of the present invention had good thermoformability, and the thermoformed product obtained from the sheet had good heat resistance and low-temperature impact resistance. On the other hand, as shown in the comparative example, if the blending ratio of C0-P and crystal nucleating agent is outside the range of the present invention, the thermoformability of the sheet,
Or the performance of the thermoformed product was poor.

Examples 8 to 10 and Comparative Examples 3 to 6 Polyester sheets were obtained in the same manner as in Example 1, except that PET was changed to one with an intrinsic viscosity shown in Table 2, and a polyolefin different from that of the present invention was used. , further Example 1
A molded body was obtained by thermoforming in the same manner as in . Table 2 shows the physical properties of the sheet and the tray.

As is clear from Table 2, in the case of a sheet with a low intrinsic viscosity of 0.6, or in the case of a sheet using a polyolefin different from that of the present invention, the thermoformability of the sheet or the performance of the thermoformed product may be affected. It was defective.

Examples 11 to 15 and Comparative Examples 7 to 8 PET pellets having an intrinsic viscosity of 0.81 were dried in the same manner as in Example 1 to obtain dry pellets. This dried pellet, Co
- After blending PP, crystal nucleating agent, and coloring agent in the proportions shown in Table 4, an extruder with a 65 mm screw diameter and a 50 mm screw diameter equipped with a die for extruding two or three layer sheets at the tip is used.
It was fed into an extruder with a screw diameter. In this case, compound A in Table 3 was supplied to the 65 mm diameter extruder, and compound 8 in Table 3 was supplied to the 50 mm diameter extruder. The extruder cylinder is melted and kneaded at a set temperature of 240 to 280°C, discharged from a die, and cooled in a cooling drum to form a wall thickness of 0.25 m.
A polyester sheet of m was obtained. Table of density of each sheet -
Shown in 3.

The sheet was thermoformed in the same manner as in Example 1, and the heat resistance, low-temperature impact resistance, and moldability of the thermoformed product thus obtained were evaluated. The evaluation results are shown in Table-3.

As is clear from the results shown in Table 3, the outer layer (Table 3
When the blending amounts of C0-PP and crystal nucleating agent in layer A) and inner layer (layer B in Table 3) are within the range of the present invention, thermoformability is good, and the obtained thermoformed product is Although the heat resistance and low-temperature impact resistance were good, as shown in the comparative example,
When the blending amounts of PP and the crystal nucleating agent were outside the range of the present invention, the thermoformability and performance of the thermoformed product were poor.

The polyolefins shown in Table 4 were used in the comparative examples shown in Table 2.

Claims (5)

[Claims] (1) 100 parts by weight of polyester (A) whose main repeating unit is ethylene terephthalate, and polypropylene (B) made by copolymerizing ethylene and maleic anhydride 1
A film or sheet made of a resin composition (I) mixed with 30 parts by weight. (2) A resin composition (I) according to claim 1 containing 0.1 to 2 parts by weight of a crystal nucleating agent (C) based on 100 parts by weight of the polyester (A). II)
A film or sheet consisting of However, crystal nucleating agents include graphite, carbon black, magnesium oxide, calcium silicate, magnesium silicate, talc, kaolin, calcium carbonate, magnesium carbonate, sodium carbonate, potassium carbonate, zinc oxide, alumina, barium sulfate, and calcium sulfate. Refers to at least one type selected from. (3) Resin composition (I) according to claim 1 or 2
Or a film or sheet made of a resin composition (III) in which the resin composition (II) contains an additive (D) such as a coloring agent. (4) Polyester (A), copolymerized polypropylene (B)
), a crystal nucleating agent (C), and an additive (D) at least two layers formed by laminating resin compositions having different mixing ratios. (5) A thermoformed article obtained by thermoforming the single-layer or multi-layer film or sheet according to any one of claims 1 to 4.