JP3203260B2 - Polyester sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent rigid polyester sheet used for a transparent case formed by bending a sheet.

[0002]

2. Description of the Related Art Unstretched amorphous polyester sheets are excellent in transparency, and are expected to be used as cases for cosmetics by bending. However,
When it is necessary to supply a printing sheet as a single sheet when processing it into a case, there is a problem that sheet slippage is poor and a supply trouble occurs in the printing press. In addition, there is also a problem that the cases after assembling are not easily slipped and the surface of the case is easily damaged.

In order to improve these problems, a method of improving the slipperiness by adding inorganic fine particles to the sheet can be considered. Of the polymer is reduced. There is also a method of applying a silicon-based compound or the like to the sheet. However, the printing ink does not adhere to the sheet or cannot be bonded at the time of assembling the case. There is also a method of spraying a slip agent on the sheet surface, but it is not preferable because the slip agent adheres to the package contents.

[0004]

According to the present invention, a non-stretched sheet in which particles are added to a polyester resin is subjected to a low-magnification stretching treatment to improve the slipperiness without impairing the transparency and the secondary workability. The gist of the invention is that a substantially non-oriented sheet containing 0.01 to 5 parts by weight of particles having an average particle diameter of 20 μm or less added to 100 parts by weight of a polyester resin in at least one direction is 1.05 to 2 parts. This is a sheet formed by punching a double-stretched polyester sheet into a predetermined shape and forming ruled lines for bending.

Hereinafter, the present invention will be described in detail. FIG. 1 is a plan view showing an example of use of the sheet of the present invention, in which a polyester sheet 1 is punched into a predetermined shape, and a ruled line 2 for bending is formed. This sheet 1 is bent from the ruled line 2,
The case is formed by bonding with the bonding allowance 3.

As a polyester resin constituting the sheet 1, the dicarboxylic acid component is composed of one or more known dicarboxylic acids such as terephthalic acid and isophthalic acid, and the diol component is a known diol component such as ethylene glycol and diethylene glycol. One or more polyester resins or a mixture of two or more of these polyester resins can be used.

Specifically, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyester comprising terephthalic acid and 1,4-cyclohexanedimethanol, or copolymerized polyester containing a small amount of a copolymer component in these esters, etc. Is preferred.

When a copolymerized polyester is used, an ethylene terephthalate component is used as a main component, and isophthalic acid is used as a copolymer component in an amount of 3 to 15 mol% of the dicarboxylic acid component.
Diol component, if necessary, diethylene glycol, polyalkylene glycol, or 1,4-
Copolyester containing cyclohexanedimethanol is preferred because it can be obtained industrially at low cost.

The intrinsic viscosity of the polyester resin is preferably 0.5 or more, and if it is lower than 0.5, the impact strength of the sheet becomes weak, which is not preferable.

As particles having an average particle diameter of 20 μm or less uniformly dispersed in a polyester resin, for example, silica,
Inorganic particles such as titanium oxide, calcium carbonate, iron oxide, aluminum oxide, calcium oxide, and magnesium oxide or mixtures thereof; inorganic compounds such as talc and clay; various inert particles such as organic compounds such as high-melting organic compounds and cross-linked polymers Can be used.

It is desirable that the particles have high affinity with the polyester resin so as not to lower the transparency.
From this point, silica is particularly suitable for the ethylene terephthalate polyester resin.

The average particle size of these particles is from 0.1 to 20.
μm, particularly preferably 0.5 to 15 μm, and the addition amount is 0.01 to 5 parts by weight, preferably 0.02 to 1 part by weight based on 100 parts by weight of the polyester resin.

When the average particle diameter is less than 0.1 μm, the effect of improving the slipperiness is not so large. When the average particle diameter is more than 20 μm, the transparency of the sheet is deteriorated, and it becomes difficult to bond the sheets and to apply the ink uniformly. Here, the average particle diameter of the particles was determined by using a coulter counter (manufactured by Nippon Kagaku Kikai), and the particle diameter when the cumulative weight fraction became 50% was defined as the average particle diameter.

If the amount of the particles is less than 0.01% by weight, the effect of improving the slip property is not obtained, and if it exceeds 5% by weight, the transparency is lowered and the adhesion between the sheets is also lowered.

The method of blending the particles with the polyester resin includes a method of adding the particles at the time of polymerization and a method of mixing the resin after polymerization with a blender using a blender, and is not particularly limited. If necessary, stabilizers, lubricants, ultraviolet absorbers, pigments, and other thermoplastic resins can be added.

The resin sheet can be formed by a known technique. That is, the dried resin is supplied to an extruder, melted, extruded from a T-die into a cooling drum, and rapidly cooled to form an unstretched sheet.

Next, the unstretched sheet is supplied to a stretching machine and stretched in at least one direction. Stretching is 1.0 in one direction
Perform at a magnification of 5 times or more and 2 times or less. The preferred stretching ratio is 1.1 to 1.6 times.

By this stretching, the particles in the resin are more likely to protrude on the sheet surface, and the addition of a small amount of particles greatly improves the slipperiness. If the stretching ratio is less than 1.05, the effect of improving the slipperiness is small. On the other hand, when the ratio exceeds twice, the effect of improving the slipperiness is not so much improved, but the transparency is lowered, which is not preferable. In addition, when the film is uniaxially stretched, directionality appears in the properties of the sheet.

In the case of stretching in the biaxial direction, the stretching ratio in each direction is preferably 1.4 times or less. Stretching can be performed by a conventionally known device, but in practice, longitudinal uniaxial stretching by a roll may be simple. Although the stretching temperature depends on the type of the polyester resin, in the case of a polyester resin containing an ethylene terephthalate unit as a main component, the stretching temperature is 75 to 130 ° C.
Can be done at

In the present invention, the degree of unevenness imparted to the sheet surface can be adjusted by adjusting the particle diameter, the amount added, and the stretching ratio of the particles within the above ranges. Generally preferred surface roughness is JIS B0601
Is 0.2 to 2 μm in terms of 10-point average roughness defined by

The polyester sheet may be a multilayer sheet having a particle-added layer as a surface layer. In this case, the intermediate layer is preferably a layer to which no particles are added, from the viewpoint of increasing transparency. The materials of the surface layer and the intermediate layer are preferably the same resin in terms of interlayer adhesion, uniform stretchability, and the like, but may be a combination of different polyester resins according to the required characteristics.

Although the thickness of the present sheet is not particularly limited, it is usually about 50 to 500 μm, especially about 200 to 400 μm. In the case of a multilayer sheet, the thickness of the surface layer is 5 to 50 μm
It is good to be about.

The sheet of the present invention has improved slipperiness without impairing transparency by stretching a substantially non-oriented sheet at a low magnification of 1.05 to 2 times, particularly 1.1 to 1.6 times. And the good secondary workability of the non-oriented sheet is maintained.

[0024]

【Example】

(Example 1) To a polyethylene terephthalate pellet having an intrinsic viscosity of 0.65, 0.2 parts by weight of silica fine particles having an average particle diameter of 2.5 µm was added, and the mixture was melted by a coaxial twin-screw extruder having two vent ports. The mixture was kneaded, supplied in a fixed amount by a gear pump attached to the tip of the extruder, and extruded at 285 ° C. from a die into a sheet.

The sheet was cast on a cooling drum at 60 ° C. to form a non-stretched sheet, and then stretched in a longitudinal direction at 90 ° C. by a roll method longitudinal stretching machine at a magnification shown in Table 1 to obtain a sheet having a thickness of 250 mm.
μm polyester sheet. For comparison, a polyester sheet having a thickness of 250 μm was obtained without longitudinal stretching.

The results of measuring the transparency (haze) and the slipperiness (coefficient of friction) of the obtained sheet are shown in Table 1. The haze is in accordance with JIS K7105, and the friction coefficient is in accordance with JIS.
It was measured by K7215.

[0027]

[Table 1]

From these results, it was found that a film stretched at a draw ratio of 1.05 to 2 times had a good balance between haze and slipperiness, and the best result was obtained at a draw ratio of 1.1 to 1.6 times. Indicated. The sheet of the present invention was punched out as shown in FIG. 1, added with ruled lines, and bent, and showed good bending workability.

(Example 2) In the same manner as in Example 1, Table 2
The silica fine particles having an average particle diameter (μm) shown in Table 2 were added at the ratio (parts by weight) shown in Table 2, extruded into a sheet, and stretched 1.5 times at 90 ° C. in the length direction by a roll-type vertical stretching machine. Then, a polyester sheet having a thickness of 250 μm was obtained. For comparison, a polyester sheet having a thickness of 250 μm was obtained without longitudinal stretching. Table 2 shows the results of measuring the transparency (haze) and the slipperiness (friction coefficient) of the obtained sheet.

[0030]

[Table 2]

From the above results, it can be seen that even when the same particles are added, by stretching at a low magnification, the slipperiness can be significantly improved as compared with the unstretched sheet without impairing the transparency.

Example 3 A polyester resin containing 0.2 parts by weight of silica fine particles having an average particle diameter of 2.5 μm and a polyethylene terephthalate resin not containing silica fine particles were supplied to two single screw extruders. Then, a three-layer polyester sheet was extruded with a non-added polyethylene terephthalate resin as an intermediate layer using a T-die provided with a feed block, and was longitudinally stretched in the same manner as in Example 1 to obtain a thickness of 25%.
A sheet having a thickness of 0 μm (the outer layer was 25 μm each and the intermediate layer was 200 μm) was obtained. For the comparative example, thickness 2 without longitudinal stretching
A 50 μm sheet was obtained. Table 3 shows the results of measuring the transparency (haze) and the slipperiness (friction coefficient) of the obtained sheet.

No. Nos. 15 and 16 used polyethylene terephthalate as the outer layer. In Nos. 17 to 18, the outer layer used was a copolymerized polyester in which the acid component was composed of 80 mol% of terephthalic acid and 20 mol% of isophthalic acid, and the diol component was ethylene glycol.

[0034]

[Table 3]

The sheet of the present invention having a three-layer structure also has good slipperiness and transparency. In addition, No. 1 using the copolymerized polyester as the outer layer. No. 17 is No. 17 in slipperiness and transparency. No. 16 but almost the same. The sheet punched out from the sheet No. 17 into the shape shown in FIG. 1 can be bonded with only an organic solvent (such as tetrahydrofuran) when forming a case by bending.
Excellent in adhesiveness.

[0036]

The sheet of the present invention is formed by adding particles to a polyester resin and stretching it at a low magnification, whereby irregularities are formed on the surface even when a small amount of particles are added, and the sheet slides without impairing the transparency and the secondary workability. Properties can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a usage example of a sheet of the present invention.

[Explanation of symbols]

 1 Polyester sheet 2 Ruled line 3 Adhesion allowance

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI C08L 67/00 B65D 5/42 Z // B29K 67:00 B29L 7:00 (58) Fields surveyed (Int.Cl. ⁷ , (DB name) B29C 55/00-55/30 C08J 5/18 B65D 5/00-5/76 B65D 75/28-75/36

Claims (1)

(57) [Claims] (1) 100 parts by weight of a polyester resin,
For a substantially non-oriented sheet of the following particles with an average particle size 20μm was added 0.01 to 5 parts by weight in at least one direction
1 Preformed polyester sheet stretched from 05 to 2 times
A sheet formed by punching into a shape and forming a ruled line for bending .