JP3027461B2 - Polyester shrink film - 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 shrink film which is excellent in low-temperature heat shrinkage characteristics, mechanical strength and the like and is used for shrink labels and food packaging.

[0002]

2. Description of the Related Art Conventionally, as a shrink label used for glass bottles or polyethylene terephthalate (hereinafter referred to as PET) bottles and a shrink film for food packaging, a stretched film made of polyvinyl chloride or polystyrene is mainly used. Have been.

In recent years, however, there has been a demand for a polyester-based shrink film having excellent safety and hygiene properties, chemical resistance, and transparency. A stretched film made of polyester obtained by copolymerizing PET with neopentyl glycol or isophthalic acid, etc. (For example, Japanese Unexamined Patent Publication No.
156833, JP-A-63-202429, and JP-B-63-7573. However, these films have insufficient shrinkage performance at low temperatures of 50 to 80 ° C.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a polyester shrink film having excellent low-temperature heat shrinkage characteristics, mechanical strength and the like.

The above-mentioned object is to provide a dicarboxylic acid component as
0.5 to 5 mol% of dimer acid, terephthalic acid and / or
Or 95 to 99.5 mol% of isophthalic acid, and 5 to 15 mo of diethylene glycol as a diol component.
This is achieved by a polyester shrink film obtained by forming and stretching a copolymerized polyester containing 1%, 85% to 95% by mole of ethylene glycol and / or tetramethylene glycol.

The composition ratio of each component constituting the copolymerized polyester of the present invention is such that dimer acid as a dicarboxylic acid component is 0.5 to 5 mol%, preferably 1 to 3 mol%, and terephthalic acid and / or isophthalic acid is 95 to 95 mol%. 99.5mo
1%, preferably 97 to 99 mol%, and 5 to 15 mol of diethylene glycol as the diol component.
%, Preferably 8 to 12 mol%, of ethylene glycol and / or tetramethylene glycol of 85 to 95 mol
1%, preferably 88 to 92 mol%.

The shrink film made of the copolymerized polyester having the above composition is excellent in low-temperature heat shrinkage characteristics and is free from wrinkles, tarmi and the like, unlike heat shrink films made of other conventional polyesters when heat shrinked. It is suitable as a film.

The dimer acid of the present invention is a dicarboxylic acid composed of a dimer of unsaturated fatty acid, and the unsaturated fatty acid preferably has 18 or more carbon atoms. For example, it can be made by dimerizing oleic acid, elaidic acid, setreic acid, erucic acid, brassic acid, linoleic acid, etc. It may be a quantified one.
Moreover, these dimer acids are rather good also contain some aromatic rings or cycloalkyl rings, even those were further hydrogenated after dimerization good
No.

If the amount of dimer acid is less than 0.5 mol%, shrinkage at low temperature and uniform shrinkage cannot be obtained, and poor appearance is likely to occur. On the other hand, if it exceeds 5 mol%, stretchability becomes poor.

When the content of diethylene glycol is less than 5 mol%, a high shrinkage cannot be obtained at a low temperature of 50 to 80 ° C., while when it exceeds 15 mol%, the mechanical strength decreases.

The following copolymer components can be added to the copolymerized polyester of the present invention as long as the properties are not significantly changed.

As the dicarboxylic acid component, adipic acid,
Oxalic acid, malonic acid, succinic acid, azelaic acid, sebacic acid, phthalic acid, 5-t-butylisophthalic acid, naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid,
Cyclohexanedicarboxylic acid, 5-sulfonate isophthalic acid, and the like.

The diol component is not particularly limited as long as the polyester can be obtained by a usual production method. Propylene glycol, neopentyl glycol,
Examples thereof include hexamethylene glycol, polyalkylene glycol, 1,4-cyclohexanedimethanol, 2-alkyl-1,3-propanediol, and a diethoxy compound of bisphenol A or bisphenol S.

Further, monofunctional compounds such as oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid, benzoic acid, benzoylbenzoic acid and methoxypolyalkylene glycol, glycerin, pentaerythritol, trimethylolethane, Polyfunctional compounds such as trimethylolpropane can also be used to the extent that the product retains substantially linear macromolecules.

Further, other polyesters, other polymers, or various additives may be added without departing from the spirit of the present invention. For example, known inert external particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, lithium fluoride and the like as inorganic and organic lubricants for improving the lubricity of the film. Insoluble high-melting organic compounds and cross-linked polymers to be blended during the melt-forming of polyester resin, and formed inside polymers such as cross-linked polymers and metal compound catalysts used during polyester production, such as alkali metal compounds or alkaline earth metal compounds. There are internal particles.

If necessary, a stabilizer, a coloring agent, an antioxidant, an antifoaming agent and the like may be contained. The content of these additives contained in the film is usually 0.005 to 0.5.
5% by weight.

The intrinsic viscosity, which is a measure of the molecular weight of the copolymerized polyester of the present invention, is preferably 0.5 or more, more preferably 0.6 or more. Strength tends to decrease.

Next, the method for producing the film of the present invention will be specifically described. An unstretched sheet is produced by a known method such as an extrusion method or a calendering method using the copolymerized polyester of the present invention, and then preferably unidirectionally or bidirectionally, preferably 2.0 times or more and 5.0 times or less, more preferably. Is stretched to 2.5 times or more and 4.5 times or less, and finally has a thickness of 20 to 50 μm.
Make a stretched film of the order.

The stretching means is not particularly limited, and a method such as roll stretching or tenter stretching is applied, and the shape may be any shape such as a flat shape or a tube shape. The stretching method may be any of uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching depending on the application. The stretching temperature is
Although it is appropriately selected in view of the stretching stress and the stretched film, it is usually set at 10 from the glass transition temperature (hereinafter referred to as Tg).
It is preferable that the film is stretched at a relatively low temperature in order to obtain a low temperature heat shrinkage property at a high temperature of about 30 ° C.

[0020]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The measurement and evaluation methods are shown below.

(Intrinsic viscosity) Phenol / tetrachloroethane = 50/50
The mixture was heated and dissolved at about 110 ° C. for 1 hour, and the intrinsic viscosity (η) was measured at 30 ° C.

(Low-Temperature Heat Shrinkability) The polyester shrink film is heat-shrinked in a glycerin bath at 80 ° C. for 30 seconds under no load, and the shrinkage rate is less than 20%.
20% or more and less than 40% were rated as △, 40% or more as ○, and those with poor appearance such as wrinkles after shrinkage were rated as ×, and those with good appearance were rated as ○.

(Extensibility) The thickness of the polyester shrink film is measured, and the difference between the maximum value and the minimum value from the average value is less than 5% of the average value of the thickness.
% Was evaluated as Δ, and 10% or more was evaluated as ×.

(Tensile strength) The tensile strength of the polyester shrink film was measured at a width of 10 mm, a sample length of 40 mm and a tensile speed of 200 mm / min, and was measured to be 250 kg / cm.
Less than ² x, 250 kg / cm ² or more 500 kg / cm
Less than ² △, it was evaluated by ○ the 500kg / cm ² or more.

(Examples 1 to 5, Comparative Examples 1 to 4) First, dimethyl components of terephthalic acid and isophthalic acid were subjected to a transesterification reaction with a diol component, and then dimer acid was added to carry out an esterification reaction, followed by polymerization. In this manner, a copolymerized polyester having the composition shown in Table 1 was obtained. Next, an unstretched sheet having a thickness of about 300 μm is made by a T-die extruder, and then simultaneously biaxially stretched at 3.5 × 3.5 times at Tg + 20 ° C. to obtain a polyester shrink film having a thickness of about 24 μm. Created.

The results of the above-described evaluation of the obtained shrink film are shown in Table 2.

[0027]

[Table 1] (Note) * 1 Dimer acid A type: dimer acid having 36 carbon atoms * 2 Dimer acid B type: dimer acid having 44 carbon atoms * 3 TPA: terephthalic acid * 4 IPA: isophthalic acid * 5 DEG: diethylene glycol * 6 EG: Ethylene glycol * 7 BG: tetramethylene glycol

[0028]

[Table 2]

As shown in Table 2, a shrink film excellent in low-temperature shrinkage and tensile strength and having small thickness unevenness could be obtained in the example, but a well-balanced shrink film could not be obtained in the comparative example. .

[0030]

The polyester shrink film of the present invention is excellent in heat shrinkability at low temperatures and mechanical strength, has no defects such as uneven thickness, and is suitable for shrink packaging of shrink labels and foods.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI C08L 67/02 C08L 67/02 // B29K 67:00 105: 02 B29L 7:00 (58) Fields surveyed (Int.Cl. ⁷ , DB name) C08J 5/18 CFD C08G 63/181 C08G 63/199 C08L 67/02

Claims (1)

(57) [Claims] 1. A dicarboxylic acid component containing 0.5 to 5 mol% of dimer acid, 95 to 99.5 mol% of terephthalic acid and / or isophthalic acid, and 5 to 15 mol% of diethylene glycol, ethylene glycol and And / or 8 of tetramethylene glycol
A polyester film containing 5 to 95 mol% is formed into a film,
A polyester shrink film obtained by stretching.