JPH0732560A - Multi-ply polyester sheet - Google Patents

Abstract

PURPOSE:To provide a polyester sheet which can be cut while a large number of sheets are stacked. CONSTITUTION:For a multi-ply polyester sheet, a surface layer consisting of a resin composition, for which 3-20wt.% of a polycarbonate resin is blended to 80-97wt.% of a polyester resin, is formed on both surfaces of a transparent polyester resin base layer by a thickness of 5mum or higher. The cutting property is drastically improved by providing a thin surface layer, and at the same time, a transparency is maintained also.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer polyester sheet for use in applications such as bending a sheet to obtain a case-like body or thermoforming into a container.

[0002]

2. Description of the Related Art A polyethylene terephthalate (PET) sheet in an unstretched or amorphous state has excellent transparency as compared with a polyvinyl chloride resin sheet or an unstretched polypropylene sheet, and is easy to treat after use. So it is suitable as a transparent case for cosmetics and dolls.

In order to manufacture such a case, it is necessary to cut a large-sized sheet into a sheet of a required size (so-called cutting board sheet) and supply the sheet to a printing machine. Usually, for a hard polyvinyl chloride sheet or the like, for example, 250μ thick
In the case of m, a sheet of a required size is obtained by applying it to a cutting machine in a state where 200 to 300 large sheets are stacked.

[0004]

However, in the case of a PET sheet, when a large number of sheets are superposed and cut, the cut sheet end faces are fused and burr occurs,
This causes a problem that the cut sheets cannot be peeled off one by one. In addition, there is a problem that the sheet itself causes blocking and the cutting blade does not enter, the cutting blade is chipped or wears quickly, and when actually cutting the PET sheet into a single sheet, a small amount of paper is added to the cutting machine. Only the number of sheets must be supplied, which requires manpower and time. Also,
Also in thermoforming applications such as vacuum forming and pressure forming, it is efficient if the sheets and the like can be stacked and sheets can be cut all at once, such as cutting sheets before forming and punching containers after forming.

[0005]

According to the present invention, by forming a surface layer in which a polyester resin is mixed with a polycarbonate resin on both surfaces of a polyester sheet such as PET, transparency and secondary processability are not impaired. A sheet having improved stacking cutability of a PET sheet, and particularly, a sheet suitable as a folding sheet to be used for forming a ruled line and bending to obtain a transparent case by taking advantage of its excellent transparency. is there. That is, the gist of the present invention is to apply a polycarbonate resin in an amount of 3 to 2 to 80 to 97% by weight of the polyester resin on both surfaces of the transparent polyester resin base layer.
A surface layer made of a resin composition mixed with 0% by weight of 5 μm each
It is a multilayer polyester sheet formed with a thickness of m or more.

The present invention will be described in detail below. The base layer of the sheet of the present invention is made of a transparent polyester resin, particularly an ethylene terephthalate polyester resin. This layer is preferably not highly oriented and is substantially not crystallized (amorphous state) for secondary processing such as bending and thermoforming.

As the polyester resin, a homopolymer of ethylene terephthalate, or 60 mol% or more, preferably 90 mol% or more of the dicarboxylic acid component is terephthalic acid and 60 mol% or more, preferably 9 mol% of the diol component.
A copolymer resin in which 0 mol% or more is ethylene glycol,
Alternatively, a mixture of two or more of these polyester resins can be used.

Examples of the copolymerization component include various known dicarboxylic acids such as isophthalic acid, adipic acid and neopentylic acid, and diol components such as diethylene glycol, polyalkylene glycol, neopentyl glycol and 1,4-cyclohexanedimethanol. it can.

The ethylene terephthalate polyester resin is relatively inexpensive, can be easily formed into a sheet, and is excellent in strength, rigidity, transparency and bending workability. In most cases, the most readily available polyethylene terephthalate (homopolymer) is sufficient for the base layer,
It is also preferable in terms of characteristics. The intrinsic viscosity of these polyester resins is preferably 0.5 or more, more preferably 0.6 or more, and if it is less than 0.5, the strength of the sheet becomes low, which is not preferable.

The thickness of the polyester resin base layer can be appropriately set depending on the application, but is generally 50 to 500 μm, for example, a folding sheet has a thickness of 150 μm or more, preferably 200 to 400 μm, and its thickness range. It is preferable that the haze has a transparency of 3% or less, particularly 2% or less. This can be easily obtained by not adding a lubricant, an antistatic agent, or the like, which impairs the transparency, to the polyester resin of the base layer, or by using a sheet forming condition such that the amount thereof is small and the crystallization is not promoted. .

The surface layer of the sheet of the present invention contains 3 to 3% of polycarbonate resin with respect to 80 to 97% by weight of polyester resin.
It consists of a resin composition mixed at 20% by weight. By adding this small amount of polycarbonate resin, the cutting property of the sheet is dramatically improved.

As the polyester resin used here,
The same base layer as above can be used. In particular, as a sheet for bending, this surface layer is preferably composed mainly of an amorphous copolyester resin. In the folding process, the folded end portion of the sheet may be bonded with a solvent, but the crystalline polyester resin is crystallized and whitened by contact with the solvent. Therefore, by making the surface layer mainly amorphous copolyester resin,
Good adhesion can be achieved with a general-purpose solvent such as tetrahydrofuran without causing whitening.

The term "amorphous" as used herein means that a polyester resin or a polyester resin mixture is measured with a differential scanning calorimeter (DSC-7 type manufactured by Perkin Elmer Co., Ltd.) from a molten state.
It means that the heat of crystallization (ΔHc) when the temperature is lowered at a rate of ° C / min is 5 cal / g or less.

Examples of the amorphous copolyester resin include those containing a relatively large amount of the copolymer component as described for the polyester resin used for the base layer, and particularly ethylene terephthalate units. In the case of polyester as the main constituent, a resin containing 20 to 40 mol% of isophthalic acid in the dicarboxylic acid component, or a resin containing 20 to 60 mol% of 1,4-cyclohexanedimethanol as the diol component, etc. There is.

The polycarbonate resin to be blended with the polyester resin for the surface layer is produced by using bisphenol as a main raw material by a phosgene method or a transesterification method. The raw material bisphenol is 2,2-
Examples include bis (4-hydroxyphenyl) propane (bisphenol A) and 1,1-bis (4-hydroxyphenyl) cyclohexane (bisphenol Z).
A copolymerized polycarbonate resin containing a carboxylic acid as a copolymerization component can also be used, and for example, a resin obtained by copolymerizing a linear carboxylic acid ester such as 1,10-decanedicarboxylic acid is preferable. As the polycarbonate resin, those having an average molecular weight of 1,000 to 10,000 are preferable.

The blending amount of the polycarbonate resin is 3
-20% by weight, preferably 5-15% by weight,
If it is less than 3% by weight, the effect of improving the cutting property is small, and if it exceeds 20% by weight, the transparency is greatly lowered. The thickness of both surface layers may be about 5 μm or more on one side from the viewpoint of cutting property, but in the case of bending, etc., if the thickness is set to 20 μm or more in consideration of adhesion by a solvent, Can be prevented from penetrating into the base layer and whitening. The upper limit is preferably a thickness such that the haze of the entire multilayer sheet is less than 4%, generally 50 μm, and preferably 30.
It is about μm.

Polycarbonate resin is a resin having a relatively small decrease in transparency when blended with a polyester resin, but still a slight decrease in transparency is unavoidable. The present invention is based on the knowledge that it is possible to prevent the cutting property of the entire sheet by simply forming a thin polycarbonate resin blend layer on the surface, that is, the fusion of the sheet, the cracking of the cutting surface, the prevention of burrs, etc. The feature is that the cutting property is improved without sacrificing. In the sheet of the present invention, the cutting property is improved by the addition of a small amount of the polycarbonate resin. One of the reasons is that the polycarbonate resin generally has a high second-order transition temperature. It is presumed that the rapid decrease in viscosity is related, but the reason why it is effective only when the blend layer is thinly formed on the surface is unknown.

It is possible to add conventionally known additives to the surface layer of the sheet of the present invention to the extent that the characteristics of the present invention are not impaired. Examples of such additives include stabilizers,
Lubricants, antistatic agents, anti-ultraviolet agents, pigments, other thermoplastic resins and the like can be mentioned, and the addition of a lubricant is particularly preferable.

That is, it has been found that in the cutting of sheets, slipperiness between the sheets is one of the factors that facilitate the cutting. Therefore, it is preferable to add a lubricant to the surface layer to suppress the static friction coefficient to 0.7 or less.
Although there are various types of lubricants, according to the study of the present inventors, amides of linear fatty acids such as stearic acid and behenic acid are effective. It is preferable to add about 0.05 to 2% by weight of these lubricants to the resin of the surface layer in order to achieve both transparency and slipperiness.

In the present invention, the method of blending the polyester resin with the polycarbonate resin is a method of mixing the granular or powdery resins with a blender, or the previously blended raw materials with a kneader such as an extruder or a kneader. There are methods such as pelletization and the method is not particularly limited. The sheet of the present invention can also be produced by a method in which each layer is molded by extrusion molding or the like and laminated by heating. In that case, the adhesive layer is generally unnecessary, but may be provided. A more preferable method is a method in which each layer is coextruded using a die with a feed block, a multi-manifold die, and the like, which has an advantage that a thin surface layer is easily obtained and the productivity is good. The sheet of the present invention is preferably a non-stretched sheet that is not stretched in terms of performance and ease of sheet production. The following examples
The effect of the present invention will be clarified.

[0021]

EXAMPLES The measurement and evaluation methods in the following examples are as follows. 1) Haze According to JIS K7105. 2) Cutting property Using a cutting machine manufactured by Ito Iron Works Co., Ltd., MNC-3 type, 250 sheets were stacked and cut, and the state of the cutting surface was observed.

(Example 1) Two single-screw extruders were used, one was polyethylene terephthalate (homopolymer) having an intrinsic viscosity (IV) of 0.65, and the other was a polyester resin having a mixing ratio shown in Table 1. And a mixed resin of polycarbonate resin are supplied, with a three-layer multi-manifold die, polyethylene terephthalate is co-extruded as an intermediate layer and mixed resin as both surface layers and cast onto a cooling drum at 40 ° C. A three-layer sheet having a thickness of 25 μm and a center layer of 200 μm was prepared.

Here, the composition of each resin in Table 1 is as follows. Polyester (A) ... Polyethylene terephthalate (homopolymer) having an intrinsic viscosity of 0.65 Polycarbonate (a) ... Bisphenol A homopolymer Polycarbonate (b) ... 10% by weight of 1,10-decanedicarboxylic acid was copolymerized. Bisphenol A-Based Polycarbonate Here, 0.12% by weight of stearic acid amide as a lubricant and 100% by weight of resin component and 0.3% by weight of inorganic fine particles (silica having an average particle size of 6 μm) were added to the surface layer.
In addition, No. 1 in Table 1. For comparison, 11 to 12 are single-layer sheets (thickness: 250 μm) having only the mixed resin layer.

[0024]

[Table 1]

As is clear from the results shown in Table 1, when the surface layer is blended with the polycarbonate resin in an amount of 3% or more, the cutting property is improved, but when it exceeds 20%, the transparency is considerably lowered, and the sheet is used as a transparent sheet. You will find it difficult. The polycarbonates (a) and (b) were equivalent in cutting property, and the transparency (b) was superior in terms of transparency.

Example 2 A sheet was manufactured and evaluated in the same manner as in Example 1 except that the following amorphous polyester resin was used as the polyester resin for the surface layer. The contents and results are shown in Table 2. Polyester (B) ... Dicarboxylic acid is terephthalic acid, diol component is ethylene glycol 67 mol% and 1,4-
Cyclohexanedimethanol 33 mol% copolyester (Intrinsic viscosity 0.8, ΔHc = 0 cal / g) Polyester (C) ... Dicarboxylic acid is terephthalic acid 78
Copolymerized polyester in which mol%, isophthalic acid 22 mol%, and diol component are ethylene glycol (intrinsic viscosity 0.7, ΔHc = 0 cal / g)

[Table 2]

From the results shown in Table 2, it was found that even when the amorphous polyester resin was used as the polyester resin for the surface layer, the cutting property was improved by blending the polycarbonate resin in an amount of about 3 to 15% by weight. . In addition, in the case of this example, in addition to the cutting property, adhesion with a general-purpose solvent such as tetrahydrofuran was possible, and the solvent adhesion was excellent.

Example 3 A sheet was manufactured and evaluated in the same manner as in Example 1 except that the materials for the surface layer shown in Table 3 were used and the thickness of the surface layer was changed. The contents and results are shown in Table 3.

[0029]

[Table 3]

From the results shown in Table 3, it is preferable to blend 15% by weight of polycarbonate when the surface layer is thin (about 5 μm), and about 5% by weight of polycarbonate when the thickness is about 20 μm. However, it can be seen that the cutting property is improved. Further, the thickness of the surface layer is preferably 30 μm or less from the viewpoint of transparency, and 2 from the viewpoint of solvent adhesion.
It can be said that 0 μm is preferable.

[0031]

EFFECTS OF THE INVENTION The sheet of the present invention comprises thinly forming a surface layer comprising a resin composition in which a polycarbonate resin is mixed in an amount of 3 to 20% by weight with respect to 80 to 97% by weight of a polyester resin on both surfaces of a transparent polyester sheet. In addition, it is possible to greatly improve the cuttability in a state in which a large number of sheets are stacked, without impairing the transparency and the secondary processability of the sheets.

Claims (2)

[Claims] 1. A surface layer made of a resin composition in which a polycarbonate resin is mixed in an amount of 3 to 20% by weight with respect to 80 to 97% by weight of a polyester resin on both surfaces of a transparent polyester resin base layer, each having a thickness of 5 μm or more. A multilayer polyester sheet formed. 2. The multilayer polyester sheet according to claim 1, wherein the polyester resin of the surface layer is mainly composed of an amorphous copolyester resin.