JPH05105776A - Polyester sheet - Google Patents

Abstract

PURPOSE:To provide a polyester sheet improved in its slipping property without deteriorating its transparency and secondary processability by subjecting a non-oriented sheet comprising a polyester and fine particles to a low ratio orientation treatment. CONSTITUTION:A non-oriented polyester sheet containing fine particles such as silica or titanium oxide particles having an average particle size of <=20mum in an amount of 0.01-5 pts.wt. based on the polyester resin is subjected to an orientation treatment at an orientation ratio of 0.05-2 times to provide the objective transparent rigid polyester sheet 1 suitable for transparent cases, etc.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Non-stretched amorphous polyester sheets are excellent in transparency, and are expected to be used as a case for cosmetics by bending. However,
It is necessary to supply the sheet as a sheet to the printing machine when processing the case, but there is a problem that the sheet slips badly and a supply trouble occurs in the printing machine. In addition, there is a problem that the cases are not slippery after the assembling and the surface of the cases is easily scratched.

In order to improve these problems, a method of improving the slipperiness by adding inorganic fine particles to the sheet is conceivable. However, the effect of improving the slipperiness is small if it is simply added, and if the addition amount is increased, the sheet is increased. Transparency is reduced. There is also a method of applying a silicon compound or the like to the sheet, but the printing ink does not adhere to it or the case cannot be attached during assembly. There is also a method of spraying a slip agent on the surface of the sheet, but it is not preferable because the slip agent adheres to the package contents.

[0004]

According to the present invention, a non-stretched sheet obtained by adding particles to a polyester resin is stretched at a low ratio to improve slipperiness without impairing transparency and secondary processability. The gist of the present invention is to stretch a substantially non-oriented sheet obtained by adding 0.01 to 5 parts by weight of particles having an average particle diameter of 20 μm or less to a polyester resin by 1.05 to 2 times in at least one direction. It is a polyester sheet characterized in that

The present invention will be described in detail below. 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. Bend this sheet 1 from the ruled line 2,
The case is formed by adhering with a bonding margin 3.

In the polyester resin constituting the sheet 1, the dicarboxylic acid component is 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. A polyester resin composed of one kind or two or more kinds, or a mixture of two or more kinds of these polyester resins can be used.

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

When the copolymerized polyester is used, the main component is the ethylene terephthalate component, and isophthalic acid is used as the copolymerization component in an amount of 3 to 15 mol% of the dicarboxylic acid component.
And if necessary, as a diol component, diethylene glycol, polyalkylene glycol, or 1,4-
A copolyester containing cyclohexanedimethanol is preferred because it is industrially inexpensive to obtain.

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 the particles having an average particle size of 20 μm or less, which are uniformly dispersed in the polyester resin, for example, silica,
Inorganic particles such as titanium oxide, calcium carbonate, iron oxide, aluminum oxide, calcium oxide and magnesium oxide or a mixture thereof; inorganic compounds such as talc and clay; various inert particles such as high melting point organic compounds and organic compounds such as crosslinked polymers Can be used.

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

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

Particles having an average particle size of less than 0.1 μm have little effect on improving the slipperiness, while particles having an average particle size of more than 20 μm deteriorate the transparency of the sheets and make it difficult to adhere the sheets to each other and uniformly apply the ink. Here, the average particle size of the particles was determined by using a Coulter Counter (manufactured by Nippon Kagaku Kikai Co., Ltd.), and the particle size when the cumulative weight fraction was 50% was defined as the average particle size.

If the amount of the particles added is less than 0.01% by weight, the effect of improving the slipperiness will not be obtained, and if it exceeds 5% by weight, the transparency will decrease and the adhesion between the sheets will also decrease.

The method of adding particles to the polyester resin includes a method of adding during polymerization and a method of mixing the resin after polymerization with a blender, and is not particularly limited. If necessary, stabilizers, lubricants, ultraviolet absorbers, pigments, other thermoplastic resins, etc. may be added.

The resin can be formed into a sheet by a known technique. That is, the dried resin is supplied to an extruder, melted, extruded from a T-die to 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
The magnification is 5 times or more and 2 times or less. The preferred draw ratio is 1.1 to 1.6 times.

By this stretching, the particles in the resin are likely to project onto the surface of the sheet, and the slip property is greatly improved by adding a small amount of particles. When the draw ratio is less than 1.05 times, the effect of improving the slipperiness is small. Further, if it exceeds 2 times, the effect of improving the slipperiness is not improved so much, but the transparency is deteriorated, which is not preferable, and when the film is uniaxially stretched, the sheet characteristics show directionality.

When biaxially stretching, the stretching ratio in each direction is preferably 1.4 times or less. The stretching can be carried out by a conventionally known apparatus, but in practice, longitudinal uniaxial stretching with a roll may be simple. The stretching temperature depends on the type of polyester resin, but in the case of a polyester resin containing ethylene terephthalate units as the main component, the stretching temperature is 75 to 130 ° C.
Can be done at.

In the present invention, by adjusting the particle size of the particles, the addition amount and the stretching ratio within the above ranges, the degree of unevenness imparted to the sheet surface can be adjusted. Generally preferred surface roughness is JIS B0601.
The average roughness of 10 points defined by is 0.2 to 2 μm.

The polyester sheet may be a multi-layer sheet having a particle addition layer as a surface layer. In this case, it is preferable that the intermediate layer is a layer to which particles are not added in order to improve transparency. Further, the materials of the surface layer and the intermediate layer are preferably the same resin from the viewpoints of interlayer adhesion and uniform stretchability, but different polyester resins may be combined depending on the required properties.

The thickness of this sheet is not particularly limited, but is usually 50 to 500 μm, and particularly 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 set the degree.

The sheet of the present invention is improved in slipperiness without impairing transparency by stretching a substantially non-oriented sheet at a low ratio of 1.05 to 2 times, particularly 1.1 to 1.6 times. In addition, the good secondary processability of the non-oriented sheet can be maintained.

[0024]

【Example】

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

The sheet was cast on a cooling drum at 60 ° C. to obtain a non-stretched sheet, which was then stretched in the longitudinal direction at 90 ° C. by a roll-direction longitudinal stretching machine at a ratio shown in Table 1 to give a thickness of 250.
A polyester sheet of μm was used. For comparison, a 250 μm-thick polyester sheet was obtained without longitudinal stretching.

Table 1 shows the results of measuring the transparency (haze) and the slipperiness (friction coefficient) of the obtained sheet. The haze is based on JIS K7105 and the friction coefficient is JIS.
It was measured by K7215.

[0027]

[Table 1]

From these results, those drawn at a draw ratio of 1.05 to 2 times have a good balance of haze and slipperiness, and particularly the draw ratio of 1.1 to 1.6 times gives the best results. Indicated. Further, the sheet of the present invention, when punched as shown in FIG. 1, provided with ruled lines and bent, showed good bending workability.

(Example 2) In the same manner as in Example 1, Table 2
The silica fine particles having the average particle diameter (μm) shown in Table 2 were added to the ratio (parts by weight) shown in Table 2 and extruded into a sheet, and stretched 1.5 times in the length direction at 90 ° C. with a roll-direction longitudinal stretching machine. Then, a 250 μm-thick polyester sheet was formed. For comparison, a 250 μm-thick polyester sheet was obtained without longitudinal stretching. Table 2 shows the results of measuring the transparency (haze) and the slidability (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, the slip property can be significantly improved as compared with the non-stretched sheet without impairing the transparency by stretching at a low magnification.

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 containing no silica fine particles were supplied to two single screw extruders. Using a T-die with a feed block, a three-layer polyester sheet was extruded with a non-added polyethylene terephthalate resin as an intermediate layer, and longitudinally stretched in the same manner as in Example 1 to obtain a thickness of 25.
The sheet was 0 μm (each outer layer was 25 μm and the intermediate layer was 200 μm). For comparison, the thickness is 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 to 16 use polyethylene terephthalate as the outer layer, and No. In Nos. 17 to 18, as outer layers, copolymerized polyesters having an acid component of 80 mol% terephthalic acid and 20 mol% isophthalic acid and a diol component of ethylene glycol were used.

[0034]

[Table 3]

The sheet of the present invention having a three-layer structure is also excellent in slipperiness and transparency. Further, No. 1 using a copolyester as an outer layer. No. 17 is No. 17 in terms of slipperiness and transparency. Although it is almost the same as No. 16, No. 16 The sheet punched out into the shape of FIG. 1 from the sheet of 17 can be pasted with the adhesive margin 3 only with an organic solvent (such as tetrahydrofuran) when the case is formed by bending.
Excellent in adhesiveness.

[0036]

EFFECTS OF THE INVENTION The sheet of the present invention is formed by adding particles to a polyester resin and stretching at a low magnification, so that even if a small amount of particles are added, unevenness is formed on the surface of the sheet, and transparency and secondary processability are not impaired. The sex can be improved.

[Brief description of 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

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Claims (1)

[Claims] 1. A substantially non-oriented sheet in which 0.01 to 5 parts by weight of particles having an average particle diameter of 20 μm or less are added to a polyester resin is stretched 1.05 to 2 times in at least one direction. And polyester sheet.