JPH08156210A - Thermoformed polyester container excellent in slip properties - Google Patents

Abstract

PURPOSE: To impart excellent slip properties and stacking preventing properties by laminating a skin layer wherein specific inert particles and a specific ester product are compounded to a core layer composed of polyester having specific intrinsic viscosity. CONSTITUTION: A polyester polymer with intrinsic viscosity of 0.4-1.1 is synthesized by the polycondensation of a dicarboxylic acid component based on terephthalic acid and a glycol component consisting of 90-10mol% of ethylene glycol and 10-90mol % of 1,4-cyclohexane dimethanol. 0-10000ppm of inert particles wherein the particle size of secondary particles is 10μm or less and 0.01-5wt.% of an ester product of polyhydric alcohol having three or more hydroxy groups and 12 or more C aliphatic monocarboxylic acid are compounded with the polyester polymer to form a skin layer. A core layer composed of polyester with intrinsic viscosity of 0.4-1.1 is laminated to the skin layer to constitute a polyester laminate. In this case, the skin layer is laminated to at least the single surface of the core layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoformed polyester container having improved slipperiness, blocking property and stacking property without impairing processing properties such as transparency, printability and heat sealability.

[0002]

2. Description of the Related Art Saturated polyesters, especially crystalline polyester resins represented by polyethylene terephthalate (hereinafter abbreviated as PET) are widely used as polymers for sheet films including fibers, but have excellent chemical resistance. Moreover, it has come to be applied to carbonated drinks, juice, bottles for beverages such as beer, cosmetics containers, food trays, etc. by taking advantage of its low gas permeability.

Among them, the amorphous polyester sheet called A-PET has attracted attention for its excellent recyclability, low pollution and food safety, and in recent years, its amount has rapidly increased as a packaging material replacing vinyl chloride and polystyrene. There is. 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 in which cosmetics, electric devices, etc. are put.

Conventionally, containers obtained by thermoforming such saturated polyester sheets cause blocking due to the inherent adhesiveness of the polyester resin when stacked, and they can be taken out one by one when food is automatically filled. It was difficult.

Many proposals have hitherto been made on methods for improving the slipperiness of polyester. For example, JP-A-50-
Inactive particles such as silicon oxide, calcium carbonate, talc, kaolin, and wollastonite are added at the time of polymerization or as described in JP-A No. 45885, JP-A No. 4-136063, and JP-A No. 4-180957. There is a method of adding during film formation (inert particle addition method). These methods are not effective enough to prevent stacking of the container, and it is necessary to increase the amount of particles blended in order to provide sufficient slipperiness, which causes a decrease in the transparency and mechanical properties of the sheet and causes problems. Was becoming.

Further, as described in JP-A No. 53-14753, a method in which a part or all of a catalyst, a color-preventing agent and the like used in polyester polymerization is precipitated in the course of the reaction and is present as fine particles (internal particle forming method). Alternatively, JP-A-49-117550 and JP-A-57-1475.
No. 43, JP-A No. 1-110555, a method of blending a resin having a high melting point or a resin having a high Tg (resin blending method) has been proposed, but in a state where a draw ratio is low such as thermoforming. It has almost no effect on improving slipperiness.

Further, as described in JP-B-44-8759 and JP-A-60-61259, there is a method of spraying fine powder on the surface of the sheet or coating or printing a coating film having slipperiness. With these methods, uniform adhesion and coating are difficult, and thus the appearance and physical properties are likely to be impaired. Further, a method of applying silicon to the surface is widely and generally used, but the heat sealability, printability and adhesiveness are deteriorated, and the use is remarkably limited.

[0008]

DISCLOSURE OF THE INVENTION As a result of intensive studies made by the present inventors in order to solve such conventional problems, a polyester polymer having a specific composition has an inert gas having a specific secondary particle diameter. By blending particles, an ester product of a specific polyhydric alcohol and an aliphatic monocarboxylic acid in a specific ratio, A-PE in a thermoformed polyester container is obtained.
The inventors have found that excellent slipperiness and stacking prevention can be imparted without impairing the transparency, printability, and heat-sealing performance of T, leading to the present invention.

[0009]

That is, the present invention provides (A) a dicarboxylic acid component containing terephthalic acid as a main component, 90 to 10 mol% of ethylene glycol, 1,4-cyclohexanedimethanol (hereinafter referred to as 1,4-CHDM). 10)
Polyester polymer having 90 mol% of a glycol component polycondensed and having an intrinsic viscosity of 0.4 to 1.1 has an average particle diameter of secondary particles of 10 μm or less, inactive particles of 0 to 10000 ppm, and A skin layer containing 0.01 to 5% by weight of an ester product of a polyhydric alcohol having 3 or more hydroxyl groups and an aliphatic monocarboxylic acid having 12 or more carbon atoms, and (B) terephthalic acid and ethylene glycol. A polyester laminate comprising a core layer made of polyester which is polycondensed and has an intrinsic viscosity of 0.4 to 1.1, wherein the (A) layer is laminated on at least one side, and (A) layer is 1 of the total thickness of the sheet
It is a substantially amorphous thermoformed polyester container obtained by thermoforming a polyester sheet in the range of ˜50%.

The copolymerized polyester (A) to be laminated on the surface used in the present invention comprises a dicarboxylic acid component containing terephthalic acid as a main component and ethylene glycol of 90 to 10 mol% and 1,4-CHDM of 10 to 90 mol%. It is obtained by polycondensing a glycol component.

The amount of 1,4-CHDM to be copolymerized is preferably 15 to 85 mol%. When it is less than 10 mol% or more than 90 mol%, the compatibility of the polyhydric alcohol compounded as the organic lubricant and the ester product consisting of the aliphatic monocarboxylic acid deteriorates and the transparency of the sheet deteriorates. It is not preferable because

The polyester (B) used in the core layer of the present invention is not limited to PET, but a part of the terephthalic acid component is isophthalic acid, adipic acid, diphenylcarboxylic acid,
Substituting one or more other dicarboxylic acid components such as diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, sebacic acid, naphthalene dicarboxylic acid, etc., and part of the ethylene glycol component is diethylene glycol, hexamethylene glycol, trimethylene glycol, propylene glycol, It includes copolyesters substituted with one or more other glycol components such as cyclohexanedimethanol, neopentyl glycol, butylene glycol and the like.

The total proportion of the copolymerization components in the polyester (B) is preferably 40 mol% or less based on the total acid components. Further, a compound having three or more functional groups or a monofunctional compound may be contained within the range considered to be substantially linear. Further, 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 reduce the transparency. Further, when matting is required, a coloring agent such as titanium dioxide, calcium carbonate, iron oxide or carbon black may be contained.

The intrinsic viscosity of the polyester (B) used in the core layer of the present invention is measured at 20 ° C. in a phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40.
The intrinsic viscosity needs to be 0.4 to 1.1, and is preferably 0.6 or more. If it is less than 0.4, the mechanical strength of the final product, especially the impact strength at low temperature, is insufficient. On the other hand, when the intrinsic viscosity is more than 1.1, not only the economical efficiency is deteriorated but also the melt moldability at the time of film formation is deteriorated.

The thickness of the sheet used in the present invention is not particularly limited, but is usually 50 to 1500 μm, preferably 15
It is 0 to 800 μm.

The inert particles used in the present invention are talc, silica, calcium carbonate, alumina, wollastonite, kaolin, zinc oxide, barium sulfate, calcium phosphate, aluminum hydroxide, Ca, Ba, Zn and M.
Examples thereof include terephthalic acid metal salts such as n or crosslinked particles of polymers, and particles having a refractive index close to that of amorphous polyester are advantageous in terms of transparency.

These may be used alone or in combination, or may be added as a slurry at the time of polymerization in order to uniformly disperse them in the sheet, or within a range not deteriorating the transparency of the sheet, olefin wax, fatty acid, and metal salt of fatty acid. The surface treatment of the particles may be carried out by, for example, In order to prevent the occurrence of scratches due to the friction of the sheet, inert particles having a Mohs hardness of 5 or less, such as polystyrene (hereinafter referred to as PS)
It is effective to use crosslinked particles such as or methyl methacrylate.

The average particle diameter of the secondary particles of the inert particles is 10
Fine particles of 0 to 10000 ppm, which is less than or equal to μm, are required, the preferable particle diameter is 1 to 8 μm, and the compounding amount is 100pp
It is m-3000 ppm.

When the average particle diameter of the inert particles exceeds 10 μm or the amount of the inert particles exceeds 10000 ppm, the transparency of the container is deteriorated and scratches when superposed are remarkably undesirable. The smaller the particle size of the inert particles, or the smaller the blending amount, the more advantageous it is for maintaining the transparency of the container, but if the particle size is extremely small, for example, if it is smaller than 0.05 μm, or if the blending amount is significantly small, For example, when the content is 50 ppm or less, the slipperiness tends to be slightly deteriorated.

The ester product used in the present invention must be composed of a polyhydric alcohol having 3 or more hydroxyl groups and an aliphatic monocarboxylic acid having 12 or more carbon atoms. An ester composed of an alcohol having less than 3 hydroxyl groups of a polyhydric alcohol has a good compatibility with the above polyester, and therefore the amount of bleed-out on the surface of the sheet is small and sufficient slipperiness cannot be provided. Examples of the polyhydric alcohol having 3 or more hydroxyl groups include glycerin, pentaerythritol, sorbitol, xylitol, mannitol and the like.

When the aliphatic monocarboxylic acid used to obtain the ester product has less than 12 carbon atoms, the heat resistance of the ester product is insufficient, and when it is compounded in PET or the like, it is formed into a sheet. Not only the sliding effect becomes very low due to hydrolysis caused by heating during film formation, but also the mechanical properties of the sheet itself become very low.

Examples of such aliphatic monocarboxylic acids having 12 or more carbon atoms include tridecyl acid, myristic acid, pentadesilyl acid, palmitic acid, margaric acid, stearic acid, nonadesilyl acid, arachidic acid, heneisancoic acid, behenic acid, tricosane. Examples thereof include acids, lignoceric acid, pentacosanoic acid, cerotic acid, heptacosanoic acid montanic acid, nonacosanoic acid, and melissic acid.

The amount of the ester product required to impart good slipperiness to the sheet is 0.01 to 5% by weight, preferably 0.3 to 3% by weight. The blending amount is 0.
If it is less than 01% by weight, sufficient slipperiness cannot be provided. On the other hand, if the blending amount exceeds 5% by weight, the bleed-out amount on the surface of the sheet is too large, so that the workability such as printability and adhesiveness is significantly reduced and the transparency is impaired.

Among the esters formed from the polyhydric alcohol and the aliphatic monocarboxylic acid, compounds containing two or more ester bonds are preferable in terms of heat resistance.

The sheet can be obtained by melt-extruding using a conventional extruder for polyester such as a single-screw extruder or a twin-screw vent extruder, and cooling the molten resin with a cooling drum. The sheet is preferably cooled as rapidly as possible in order to prevent a decrease in transparency due to crystallization, the crystallinity measured by a density method is 10% by weight or less (density 1.348 or less), and the sheet haze is 5%.
The following is desirable.

As the 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, but the touch roll method is preferable from the viewpoint of glossiness and thickness uniformity of the sheet. . A known method can be applied to the method of adding the inert particles to be mixed with the polyester or the ester formed from the polyhydric alcohol and the aliphatic monocarboxylic acid, and there is no particular limitation. For example, the components are preliminarily uniformly blended with a tumbler or a blender, and the mixture is fed to an extruder, or the components to be added to the polyester are preliminarily pelletized as a masterbatch and fed at the time of extrusion, polymerization. There is a method to add it sometimes.

Further, when a multilayer sheet having two or more layers is formed, it can be produced by known techniques such as melt lamination, coextrusion and dry lamination, but coextrusion is preferable from the quality of the sheet. The ratio of the skin layer of the sheet to the total thickness of the sheet is 1 to 50%, but 3 to 20% is preferable from the viewpoint of economy and stability of quality. When the proportion of the skin layer is less than 1%, it becomes difficult to uniformly form the skin layer containing the inert particles and the ester of the polyhydric alcohol and the monocarboxylic acid at a high concentration, and slipperiness and the like are deteriorated. Be stable. On the other hand, the skin layer is 50%
Even if it is increased, the slipperiness is not further improved, and the transparency of the sheet tends to be lowered, which is not preferable.

In the present invention, the excellent recyclability inherent in A-PET is maintained, and the ears of the sheet generated during the film formation of the sheet or the skeleton generated during the punching process are crushed and the sheet is re-processed. It can be used as a raw material. These recycled raw materials can be returned to both the skin layer and the core layer of the product of the present invention.
However, when returning to the core layer, the concentration of the inert particles and the fatty acid ester contained in the core layer needs to be 50% or less of the amount blended in the skin layer. It is necessary that the concentration of the inert particles and the fatty acid ester contained by returning the recycled raw material be 50% or less of the amount blended in the skin layer. When the concentration of the inert particles and the fatty acid ester contained by returning the recycled raw material exceeds 50% of the skin layer, the transparency of the sheet is significantly lowered, which is not preferable.

The slipperiness and antiblocking property of the container are related to the performance of the sheet surface portion, and the skin layer contains a higher concentration of inert particles and the ester of a polyol and a monocarboxylic acid than the core layer. A multilayer structure is desirable.
Compared to the skin layer, the core layer contains a smaller amount of the inert particles and the ester of the polyhydric alcohol and the monocarboxylic acid, so that the transparency and mechanical properties of the container can be maintained.

[0030]

INDUSTRIAL APPLICABILITY The container of the present invention is excellent in slipperiness, blocking resistance, heat sealability and adhesiveness with an easy peeling material without impairing processing characteristics such as transparency and printability, and food packaging. Most suitable as container and blister container.

Further, it is possible to solve a variation in quality such as blocking caused by coating unevenness and insufficient peel strength, which have been problems in conventional silicon coating widely used, and to obtain a slippery thermoforming container of extremely stable quality. it can.

Further, the present invention can be obtained by the thermoforming method similar to that of the conventional A-PET. The thermoforming method used is vacuum forming, pressure forming, hot plate forming, plug assist forming, reverse draw forming, air slip forming, or the like, or a combination of these is considered to be the usual method. Can be used.

[0033]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
Each characteristic value was measured according to the following method.

(1) Container Haze Using a haze meter NDH-20D manufactured by Nippon Denshoku Co., Ltd., the haze (cloudiness value) of the bottom of the container was measured by a method according to JIS-K-7105.

(2) Blocking property 20 thermoformed containers were stacked, and a load of 2 kg was applied thereon and left for 2 days. After that, a container that dropped by its own weight was dropped, and a container that did not fall by its own weight was rated as x.

(3) Heat-sealing property The sheets were adhered to each other at 180 ° C. for 2 seconds at a pressure of 2 kg / cm ² , and the heat-sealing strength was measured by the method according to JIS-K-6772. Seal strength exceeding 500 g / 15 mm is ○,
For 200 to 500 g / 15 mm, △, 200 g /
Those having a length of less than 15 mm were marked with x.

(4) Average particle size MULTI made by Coulter Electronics Limited
The diameter (particle diameter) with an integrated volume fraction of 50% in the equivalent spherical distribution measured by the SIZER device was taken as the average particle diameter.

(5) Drop strength of container 3 in a cup-shaped container having a diameter of 130 mm and a depth of 70 mm
30 g of water was put therein, the lid was closed (mating lid), and it was dropped on the concrete surface from a height of 1.5 m for evaluation. Those that did not crack at all were rated as ◯, those with a cracking probability of 10% or less were rated as Δ, and those with a cracking probability greater than 10% were rated as x.

Examples 1 to 7 and Comparative Examples 1 to 11 When measured at 20 ° C. in a phenol / tetrachloroethane mixed solvent having a weight ratio of 60/40, the intrinsic viscosity was 0.70.
Copolymerized PET (30 mol%, 1,4 CHDM) was dried to a water content of 200 ppm or less, and the inert particles having the particle size shown in the examples were PE-treated at 270 ° C. with a biaxial kneader.
It was melt-kneaded with T resin to prepare a 2 wt% master. Similarly, a 10 wt% master of the ester product of the polyol and the aliphatic monocarboxylic acid shown in the examples was prepared. Two
When the melt extrusion is performed from a T-die using a twin-screw vented extruder under the conditions of 85 ° C. and the degree of vacuum of the vent portion is 5 mmHg, when the film is formed by the touch roll method, the master of these inert particles and ester is used. Was mixed with the polyester resin described in the example to produce a three-layer structure sheet having a composition shown in the example having a thickness of 500 μm and evaluated.

Next, the above sheet was preheated to a temperature not lower than the glass transition temperature but not higher than the melting point, and a cup-shaped container having a diameter of 130 mm and a depth of 70 mm was prepared and evaluated by a vacuum forming machine equipped with a female mold whose temperature was adjusted to 45 ° C. I went.

[0041]

[Table 1]

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B65D 1/09 C08K 5/10 KJV 7/16 KKF C08L 67/02

Claims (2)

[Claims] 1. A dicarboxylic acid component containing (A) terephthalic acid as a main component and a glycol component in a proportion of 90 to 10 mol% of ethylene glycol and 10 to 90 mol% of 1,4-cyclohexanedimethanol are polycondensed, and Inert particles having an average viscosity of secondary particles of 10 μm or less in a polyester polymer having an intrinsic viscosity of 0.4 to 1.1
A skin layer containing 0.01 to 5% by weight of an ester product of a polyhydric alcohol having 10000 ppm and 3 or more hydroxyl groups and an aliphatic monocarboxylic acid having 12 or more carbon atoms, (B) terephthalic acid and ethylene A polyester laminate comprising a core layer made of polyester that is polycondensed with glycol and has an intrinsic viscosity of 0.4 to 1.1, wherein the (A) layer is laminated on at least one side, And the layer (A) has a thickness of 1 to 50 of the entire sheet.
A substantially amorphous thermoformed polyester container obtained by thermoforming a polyester sheet in the range of%. 2. The thermoformed polyester container according to claim 1, wherein the concentration of the particles of the core layer (B) and the fatty acid ester is 50% or less of the concentration of the particles of the skin layer (A) and the fatty acid ester. .