JP3048075B2 - Polyester sheet with excellent slipperiness - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester sheet excellent in slipperiness, and more particularly to a polyester sheet excellent in slipperiness of a wrap.

[0002]

2. Description of the Related Art Generally, crystalline polyester resins represented by polyethylene terephthalate (PET) are widely used as polymers for sheets and films, including fibers. Further, by utilizing its excellent chemical resistance and low gas permeability, it has been applied to beverage bottles such as carbonated beverages, juices and beers, cosmetic containers, food trays and the like.

[0003] Above all, molded articles obtained by thermoforming a sheet made of polyethylene terephthalate are widely used as containers for foods and the like. However, a molded article made of polyethylene terephthalate has no slipperiness with respect to the wrap, so that it is impossible to wrap the molded article with a packaging machine.

Heretofore, as a method for improving the slipperiness of a polyester molded article and preventing blocking between the molded articles, there have been known a method of uniformly dispersing inert particles such as silica in polyester or a method of dispersing silicone oil on the surface of a polyester sheet. For example, a method of applying such a material or uniformly dispersing a polyolefin resin in polyester is known.

[0005] However, in a method in which inert particles such as silica are blended into polyester and the sheet surface is made uneven to improve slipperiness, blocking can be prevented but lap slipperiness is insufficient. Poor lap sliding property at the edge of molded container. Also, the method of applying silicon oil or the like does not provide sufficient lap sliding property.

[0006] Further, a polyolefin resin is uniformly dispersed in polyester to form irregularities on the sheet surface.
The method of making polyolefin with better slip than ET is
When the polyolefin-based resin is used in an amount of 10% by weight or more, a sheet excellent in lap sliding property can be obtained. However, when the amount of the polyolefin-based resin is large, excellent low gas permeability of the polyester is impaired, and furthermore, odor of olefin and the like is deteriorated. Problems come up.

[0007]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to solve such conventional problems, and as a result, by mixing a predetermined amount of a polyolefin resin and inert particles with polyethylene terephthalate. The present inventors have found that excellent lap sliding property can be imparted, and have reached the present invention.

That is, the object of the present invention is to
An object of the present invention is to provide a polyester sheet which is excellent in the slidability of a wrap. Still other objects will be apparent from the description below.

[0009]

The object of the present invention is to provide a polyethylene terephthalate of 91 to 96% by weight, a low density polyethylene and / or a linear low density polyethylene of 3 to 8% by weight and an average particle size of 1.5 to 30 μm. 0.0 inert particles
This is achieved by a polyester sheet obtained by melt-extruding a resin composition containing from 0.05 to 0.1% by weight .

Hereinafter, the present invention will be described in detail. The intrinsic viscosity of the above poly (ethylene terephthalate) is preferably 0.5 to 1.2, as measured in a phenol / tetrachloromethane mixed solvent having a weight ratio of 60/40 at 20 ° C.
6 or more is more preferable.

When the intrinsic viscosity is less than 0.5, the mechanical strength of the product after thermoforming is not sufficient, and the impact strength particularly at low temperatures tends to be extremely low. On the other hand, when the intrinsic viscosity exceeds 1.2, thermoforming tends to be difficult. Also, the blending amount of polyethylene terephthalate is
91 to 96% by weight.

The polyolefin resin used in the present invention is:
Low density polyethylene and / or linear low density polyethylene
It is. Among them, a high-molecular-weight linear low-density polyethylene is preferable, and when this is used, a polyester sheet having three-dimensional irregularities can be obtained.

The compounding amount of the polyolefin resin is 3 to 8
% By weight. If the content is less than 3% by weight, it is difficult to greatly improve the lap sliding property even if inert particles are used in combination. On the other hand, if it exceeds 8% by weight, the excellent fragrance retention of polyethylene terephthalate is lost,
Olefin odor problems occur.

[0014] the inert particles used in the present invention include silica, kaolin, Baie bentonite, talc, calcium carbonate, and the like. Among them, silica is preferably used.
The size of the inert particles is preferably 1.5 to 30 μm, more preferably 2 to 20 μm in average particle diameter (diameter).
It is.

It is necessary that the content of the inert particles is 0.005% by weight or more. If the amount is less than 0.005% by weight, it is difficult to greatly improve the lap sliding property even if a polyolefin resin is used in combination. Preferably, the content is 0.01% by weight or more. In addition, since it is difficult to uniformly disperse the particles when the amount of the inert particles increases, the amount of the inert particles is preferably 0.1% by weight or less.

The resin composition of the present invention may contain additives, antistatic agents, ultraviolet absorbers, heat stabilizers and carbon black, mica, titanium dioxide, as long as the essential properties of the polymer are not changed. If necessary, inorganic particles such as alumina and wollastonite, pigments, and the like may be appropriately contained.

The method of obtaining a polyester sheet by blending the above three components is particularly effective when carried out, for example, by the following method. That is, first, a polyolefin resin and inert particles are mixed with a tumbler or a blender,
This mixture is supplied to a kneader, melted , extruded and pelletized to obtain a master pellet. Then this master
Mixing the over pellets of polyethylene terephthalate,
After being melted and extruded by an extruder, the mixture is quenched to obtain an amorphous polyester sheet.

As described above, when the master in which the polyolefin resin and the inert particles are pelletized in advance is used, the polyolefin resin is dispersed in an island form in the polyethylene terephthalate matrix, and the inert Since the particles have irregularities, a polyester sheet having extremely excellent slipperiness can be obtained.

Further, polyethylene terephthalate, polyolefin resin, and inert particles may be mixed at a time. In this case, the polyolefin resin is dispersed in a polyethylene terephthalate matrix in an island shape, but the irregularities of the inert particles are not uniform. Because it comes out irregularly, the lap slipperiness is
It is inferior to that by the above method.

[0020] The thickness of the polyester sheet is usually 0.1.
1 mm to 3 mm, preferably 0.15 mm to 2 mm. The polyester sheet thus obtained is further formed into a desired molded product by thermoforming, for example, pressure forming, vacuum forming, compression forming, etc., and is used for various purposes.

[0021]

As described above, the polyester sheet of the present invention is excellent in lap slipperiness because the polyolefin resin and the inert particles are three-dimensionally blended with polyethylene terephthalate. Excellent in printability, low gas permeability and mechanical properties, and can be optimally used for food containers and the like.

Hereinafter, the present invention will be described specifically with reference to examples. In addition, each evaluation was performed as follows. 1. Coefficient of friction: Measures the coefficient of friction between sheet and wrap
(Less than 2.0 is good) . 2. Impact strength: 200 g of water was put in a container, covered with wrap, left at -30 ° C for 24 hours, and then dropped on a concrete floor surface with the side of the container facing down. X when less than 60 cm, 60-100 cm
Was evaluated as Δ, and at 100 cm or more as 以上. 3. Flavoring component adsorption: The limonene aqueous solution was put in a container, the wrapped product was allowed to stand at 40 ° C. for one week, and then the amount of limonene in the limonene aqueous solution was checked. …: The amount of limonene hardly decreased, and limonene was not adsorbed. ×: A decrease in the amount of limonene was observed, and limonene was adsorbed.

Examples 1, 2 and Comparative Examples 1 to 3 A pellet of polyethylene terephthalate having an intrinsic viscosity of 0.65 measured at 20 ° C. in a phenol / tetrachloromethane mixed solvent having a weight ratio of 60/40 was mixed with water 0.01% by weight
It was dried to the following. On the other hand, a polyolefin resin shown in Table 1 and silica as an inert particle (average particle size of 4) were used.
μm), and the mixture was fed to a kneader, melt-extruded and pelletized.

Next, the polyethylene terephthalate pellets and the master of the polyolefin resin and the inert particles were weighed and mixed so as to have the composition shown in Table 1.
A 0.5 mm thick polyester sheet was obtained with a single screw extruder having a diameter of 75 mm provided with a T die. The obtained polyester sheet is preheated to a temperature equal to or higher than the glass transition point and equal to or lower than the melting point.
Was prepared, and the above items were tested.

Example 3 Polyethylene terephthalate, low density polyethylene and silica were mixed and pelletized. The pellets were used as a master, mixed with polyethylene terephthalate pellets to have the composition shown in Table 1, and a polyester sheet was obtained using a single screw extruder. The obtained sheet was molded and tested in the same manner as in Example 1. Table 1 shows the results of Examples 1 to 3 and Comparative Examples 1 to 3.

[0026]

[Table 1]

From the above results, the slipperiness (friction coefficient), impact strength, and the like of the containers of the examples were good. On the other hand, the container of the comparative example had poor slipperiness (friction coefficient) and had problems in impact strength and adsorption of flavoring components.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-77548 (JP, A) JP-A-2-269761 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 67/02 C08K 3/00 C08J 5/18

Claims (1)

(57) [Claims] 1. Polyethylene terephthalate of 91 to 9
6% by weight, 3 to 8% by weight of low-density polyethylene and / or linear low-density polyethylene and average particle size of 1.5 to 30 μm
A polyester sheet excellent in slipperiness, obtained by melt-extruding a resin composition containing 0.005 to 0.1% by weight of m inert particles.