KR101594540B1 - White porous heat-shrinkable polyester-based film - Google Patents

Abstract

The present invention relates to a resin composition comprising a polyester resin, an inorganic particle, a polymer resin which is incompatible with a polyester resin, a polymer resin which is incompatible with the polyester resin, and a polymer resin particle which is crosslinked with an incompatible and amorphous polyester resin, By weight based on the total weight of the film, and the sum of the content of the polymer resin and the crosslinked polymer resin particles is 3 to 20% by weight, based on the total weight of the film, of the white porous heat-shrinkable polyester Based film, the white porous heat-shrinkable polyester film according to the present invention has an apparent specific gravity of less than 1.0, and thus can be easily separated from PET bottles due to the specific gravity difference in water when used as a label, and is useful for recycling PET bottles . Further, in the case of the conventional porous heat-shrinkable film of the multi-layered structure, the respective structural layers are respectively melted and extruded, kneaded and further melt-extruded, while the film according to the present invention is prepared by mixing the respective raw materials in a compounding manner, It can be extruded into a single layer, which simplifies the manufacturing process.

Description

WHITE POROUS HEAT-SHRINKABLE POLYESTER-BASED FILM}

The present invention relates to a white porous heat-shrinkable polyester film, and more particularly, to a white porous heat-shrinkable polyester film which is low in apparent specific gravity and excellent in heat shrinkage and light transmittance and suitable as a label for PET bottles.

BACKGROUND ART [0002] As a heat-shrinkable film, particularly a heat-shrinkable film for labeling a bottle body, films such as polyvinyl chloride and polystyrene have been mainly used. However, the polyvinyl chloride film has a problem of discharging chlorine-based gas when it is incinerated after being discarded, and the polystyrene film has a problem that it is difficult to print, and in recent years, a heat-shrinkable polyester film has attracted attention.

The heat-shrinkable polyester film has such characteristics as high heat resistance, weather resistance, easy burning, excellent printability, and can be very useful as a label. However, the heat shrinkable polyester film has an apparent specific gravity (about 1.3) similar to that of PET bottles, and it is difficult to separate PET bottles from each other by using the specific gravity difference between the containers and labels in the water when recycling PET bottles.

As a method for improving this, a porous heat-shrinkable polyester film has been proposed. Korean Patent No. 10-1117125 discloses a white porous polyester film comprising a polyester resin, a crystalline polymer resin which is non-compatible with polyester, inorganic particles, a brightener and a stabilizer, and Korean Patent No. 10-1220225 Wherein the polymer resin particle comprises a polyester resin, an inorganic particle, and a crosslinked polymer resin having an average particle diameter of 0.1 to 10 μm which is incompatible with the polyester resin and incompatible with the polyester resin, Discloses a white porous polyester film in which the content of resin particles is 1 to 15 wt% based on the total film weight. However, the polyester films do not achieve a low apparent specific gravity.

Accordingly, an object of the present invention is to provide a heat-shrinkable film for labels which is excellent in heat shrinkage and light transmittance and low in apparent specific gravity, and can be easily separated from the container due to the specific gravity difference in water.

In order to achieve the above object, the present invention provides a resin composition comprising (a) a polyester resin, (b) an inorganic particle, (c) a polyester resin and an incompatible and crystalline polymer resin, and (d) Wherein the content of the inorganic particles is 1 to 10% by weight based on the total weight of the film, and the sum of the content of the polymer resin and the crosslinked polymer resin particles is Based on the total weight of the heat-shrinkable polyester film, 3 to 20% by weight based on the total weight of the heat-shrinkable polyester film.

Since the white porous heat-shrinkable polyester film according to the present invention has an apparent specific gravity of less than 1.0, it can be easily separated from PET bottles due to the specific gravity difference in water when used as a label, and is useful for recycling PET bottles. Further, in the case of the conventional porous heat-shrinkable film of the multi-layered structure, the respective structural layers are respectively melted and extruded, kneaded and further melt-extruded, while the film according to the present invention is prepared by mixing the respective raw materials in a compounding manner, It can be extruded into a single layer, which simplifies the manufacturing process.

The white porous heat-shrinkable polyester film according to the present invention comprises (a) a polyester resin, (b) an inorganic particle, (c) a polyester resin and an incompatible and crystalline polymer resin, and (d) a polyester- Resin and non-compatible non-crystalline crosslinked polymer resin particles.

Hereinafter, components constituting the white porous heat-shrinkable polyester film of the present invention will be described in detail.

One. Polyester-based  Suzy

The polyester resin used in the present invention is a polyester homopolymer resin, a polyester copolymer resin or a blending resin thereof.

The polyester homopolymer resin is obtained by polymerizing an acid component comprising an aromatic dicarboxylic acid as a main component and a glycol component containing an alkylene glycol as a main component as polyethylene terephthalate (PET), polyethylene naphthalate (PEN) And then polymerizing it. Examples of the aromatic dicarboxylic acid include aromatic dicarboxylic acids such as dimethylterephthalic acid, terephthalic acid, isophthalic acid, dimethyl-2,5-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, Carboxylic acid, anthracenedicarboxylic acid, and?,? - bis (2-chlorophenoxy) -ethane-4,4-dicarboxylic acid. Examples of the alkylene glycol include ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and hexylene glycol.

In one embodiment of the present invention, the polyester homopolymer resin may contain, in addition to the aromatic dicarboxylic acid and the alkylene glycol described above, a second alcohol component imparting different amenability to the film. The second alcohol component may impart thermal shrinkage and seaming properties to the film. The second alcohol component may be a diol component or an alcohol component having a valence of three or more. However, any component that can lower the crystallinity of the film by lowering the crystallization of the stretch in the stretching process of the heat shrinkable film can be used. 1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-butyl- 1,2-pentanediol, 1,1-dimethyl-1,5-pentanediol, diethylene glycol, 1, , 4-cyclohexanediol, or a mixture thereof may be used. The second alcohol component may be contained in an amount of 0 to 30 mol%, 0.5 to 30 mol%, or 3 to 30 mol% based on the total amount of all alcohol components including the glycol component.

The above-mentioned polyester homopolymer resin can be produced by polymerization by all conventional methods. For example, a polyester is obtained by a direct esterification method in which a dicarboxylic acid and a diol are directly reacted, an ester exchange method in which a dicarboxylic acid dimethyl ester is reacted with a diol, and the like. The polymerization may be carried out by any of batchwise and continuous methods.

On the other hand, in order to obtain a heat-shrinkable polyester film having a high heat shrinkage ratio and excellent shrink finishing property, neopentyl glycol or cyclohexane dimethanol is contained in an amount of 10 mol% or more based on 100 mol% of the total alcohol component including glycol components By mole or more, and more preferably 14% by mole or more. The upper limit of the above-mentioned components is not particularly limited, but if it is excessively high, the heat shrinkage rate excessively becomes too high or the rupture resistance of the film may deteriorate. Therefore, it is preferably 40 mol% or less, more preferably 35 mol% And particularly preferably 30 mol% or less.

The polyester-based resin used in the present invention can be used in an amount of 60 to 90% by weight based on the total weight of the film. When the polyester-based resin is in the above range, a smooth drawing process can be performed. Desired physical properties can be realized.

2. Inorganic particles

The inorganic particles used in the present invention function to adjust the light transmittance of the film to a specific small range, for example, 40% or less, thereby imparting light ray cuttability to the film.

Examples of the inorganic particles include kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium dioxide, calcium phosphate, carbon black, and mixtures thereof. Of these, titanium dioxide particles are preferable from the viewpoint of efficiently imparting light beam cutting property.

The inorganic particles may be used in an amount of 1 to 10% by weight based on the total weight of the film. When the inorganic particles are used in an amount of 1% by weight or more, sufficient ray-cut property can be obtained. When the inorganic particles are used in an amount of 10% by weight or less, the strength of the film and the increase in apparent specific gravity can be suppressed.

The average particle size of the inorganic particles may be in the range of 0.001 to 3.5 mu m (measured by the Coulter counter method), preferably in the range of 0.005 to 3.0 mu m. When the particle diameter of the inorganic particles is within the above-mentioned range, it is possible to achieve excellent light beam cutting property and to prevent the problem that the smoothness of the surface of the film is lowered and printing is missed.

On the other hand, titanium dioxide used as an inorganic particle preferred in the present invention is classified into anatase type and rutile type crystal form. The average particle size of the anatase type is generally 2.0 占 퐉 or less, and the average particle size of the rutile type is 2.0 占 퐉 or more. In order to conceal visible light, an average particle diameter of 2.0 to 3.0 mu m is most effective, and rutile type titanium dioxide is generally more concealing than anatase type. The anatase type tends to cause yellowing or resin deterioration due to direct sunlight or the like, and is used after a special treatment (alumina, silica, organic, etc.) on the surface of titanium dioxide when used outdoors.

3. Polyester-based  Resin and Incompatible  Crystalline polymer resin

The polyester resin used in the present invention and the incompatible and crystalline polymer resin serve to control the apparent specific gravity of the film to 0.7 or more and less than 1.0 by forming pores (also referred to as voids) in the film. That is, the white porous heat-shrinkable polyester film according to the present invention is produced by mixing the polyester-based resin with a polymer resin which is incompatible and crystalline and then stretching the polyester-based resin in at least one axial direction to form pores .

Examples of the polymer resin that is incompatible with the polyester resin include a polystyrene resin, a polyolefin resin, a polyacrylic resin, a polycarbonate resin, a polysulfone resin, a cyclic olefin resin, and a cellulose resin And preferably a polystyrene-based resin can be used. Specifically, the polystyrene-based resin refers to a thermoplastic resin containing a polystyrene structure as a basic component, and may be a homopolymer such as an atactic polystyrene, a syndiotactic polystyrene, or an isotactic polystyrene, A modified resin such as an impact resistant polystyrene resin, a heat resistant polystyrene resin or a modified polyphenylene ether resin, and further a thermoplastic resin having compatibility with the polystyrene type resin such as a mixture of polyphenylene ether .

The polyester resin and the incompatible and crystalline polymer resin are used together with the following polymer resin particles in an amount of 3 to 20 wt% based on the total film weight.

4. Polyester-based  Resin and Incompatible  Amorphous adult Bridged  Polymer resin particle

The polyester resin used in the present invention and the non-compatible, non-crystalline, crosslinked polymer resin particles enable uniform and sufficient pore formation in the film together with the above-mentioned polyester resin and the incompatible and crystalline polymer resin.

The polymer resin particles can be produced by crosslinking the thermosetting polymer to have high heat resistance, or by crosslinking the thermoplastic polymer with a crosslinking agent. In addition, the crosslinked polymer resin particles may have a network structure. Such cross-linked polymer resin particles are in a state of being irreversibly cured and not melted or melted during heating, and therefore are not melted or decomposed at the extrusion temperature in the extrusion process for forming a heat shrinkable film. More specifically, the polymeric resin particles retain the solid particulate phase even at the melting temperature of the polyester-based resin. As a result, the particle size distribution of the polymeric resin particles can be uniformly controlled, and the size of the pores can be easily controlled

When the crosslinked polymeric resin particles having excellent heat resistance and being monodispersed are added together with the inorganic particles in the production of the film, a dispersed phase evenly dispersed in the PET can be generated similarly to the continuous phase. That is, since the particles of small size and uniformity are dispersed in the polyester resin, the pore size formed after stretching is small and uniform, and the number of the pores is large, so that high-magnification drawing is possible and low specific gravity can be realized.

Examples of the crosslinked polymer resin particles that are non-compatible with the polyester resin include crosslinked acrylic resins, cyclic olefin copolymer resins (COC), polyurethane resins, epoxy resins, nylon resins, silicone resins, polypropylene resins, A thermoplastic polymer resin particle selected from the group consisting of a polyethylene resin, a polymethylpentene resin, a polycarbonate resin, a polyacrylonitrile resin, and a copolymer resin thereof. Among these, an acrylic resin, particularly a crosslinked polymethyl methacrylate (PMMA) resin or a copolymer resin thereof is preferable.

The crosslinked polymer resin particles may be used in an amount of 3 to 20% by weight based on the total weight of the film together with the crystalline polymer resin for emergency use, and the crosslinked polymer resin particles should be used in an amount of 2% The desired apparent specific gravity can be achieved. If the content is 15% by weight or less, the stretching magnification can be sufficiently realized and the characteristics of the heat shrinkable film such as the shrinkage ratio can be maintained.

The shape of the polymer resin particles is preferably spherical. More specifically, the ratio of the major axis diameter to the minor axis diameter of the polymer resin particles may be about 1: 1.2 to about 1.2: 1. As described above, when the difference between the major axis diameter and the minor axis diameter is not large, the size of the pores can be appropriately controlled by the polymer resin particles.

The polymeric resin particles may have an average particle diameter of about 0.1 to 10 mu m, preferably about 0.5 to 5 mu m, more preferably about 0.5 to 1.5 mu m on a D50 basis. When the average particle diameter of the polymeric resin particles is about 0.1 m or more, dispersion of particles and workability in a compounding process can be improved. When the average particle diameter is about 10 m or less, there is no problem in the drawing processability. The polymeric resin particles are preferably monodisperse particles having a uniform particle size, and more preferably have a particle size distribution of about 0.7 to 0.8.

In addition to the above-mentioned four components, the white porous heat-shrinkable polyester film according to the present invention may further contain additives such as stabilizers, colorants, antioxidants, antifoaming agents, antistatic agents and ultraviolet absorbers, if necessary. In order to improve the whiteness of the heat-shrinkable film, a fluorescent whitening agent may be further included.

The white porous heat-shrinkable polyester film according to the present invention has an apparent specific gravity of 0.7 or more and less than 1.0, and a heat shrinkage ratio in the transverse direction of 50 to 80% after 10 seconds of treatment in hot water of 80 ± 0.5 ° C.

When the film of the present invention having an apparent specific gravity of less than 1.0 is used as a label for PET bottles, it becomes easy to separate the PET bottle from the label by water specific gravity difference at the time of recycling. The white porous heat-shrinkable polyester film according to the present invention may have an apparent specific gravity of preferably 0.7 to 0.98, more preferably 0.7 to 0.95, and most preferably 0.7 to 0.93.

The white porous heat-shrinkable polyester film according to the present invention has a heat shrinkage ratio of 50 to 80% in the transverse direction of the film obtained from the following equation after 10 seconds of treatment in hot water at 80 占. , Preferably 55% to 78%, more preferably 60% to 75%.

Heat shrinkage percentage (%) = ((length before shrinkage - length after shrinkage) / length before shrinkage) x 100

If the heat shrinkage rate is 50% or more, the label is sufficiently shrunk in a narrow portion of the PET bottle, so there is no problem in labeling. If the heat shrinkage rate is 80% or less, troubles such as twisting and wrinkling of the label during shrinkage treatment can be prevented.

The thickness of the white porous heat-shrinkable polyester film according to the present invention may be about 20 탆 to 70 탆, preferably about 35 탆 to 50 탆.

In addition, the light transmittance (total light transmittance) of the white porous heat-shrinkable polyester film according to the present invention may be 40% or less, preferably 15% to 40%, more preferably 20% to 35%.

Further, the white porous heat-shrinkable polyester film according to the present invention may have a single-layer structure. That is, the inorganic particles, the polymer resin incompatible with the polyester resin, and the polymer resin particles that are non-compatible with the polyester resin and cross-linkage that is non-compatible with the polyester resin can be inserted into the base layer containing the polyester resin as a main component.

In such a white porous heat-shrinkable polyester film, pores are formed between the polyester resin and the polymer resin, and pores are formed between the polyester resin and the crosslinked polymer resin particles, Sufficiently and uniformly.

In one embodiment, the heat-shrinkable polyester film according to the present invention comprises inorganic particles in an amount of 1 to 2% by weight, the crystalline polymer resin in an amount of 1.5 to 2.5% by weight, The resin particles are contained in an amount of 12 to 14% by weight, the inorganic particles have a diameter of 2 to 3 占 퐉, and the cross-linked resin particles have a diameter of 0.7 to 0.9 占 퐉.

Hereinafter, a method for producing the white porous heat-shrinkable polyester film of the present invention will be described.

The film of the present invention is obtained by mixing (a) 1 to 10% by weight of inorganic particles based on the total weight of the polyester resin and the total film, adding thereto a polyester resin, a polymer resin incompatible with the polyester resin, Based resin particles in an amount of 3 to 20% by weight based on the total weight of the film; (b) melt-kneading and extruding the mixed resin composition to obtain an unstretched film; And (c) biaxially stretching the unstretched film longitudinally and transversely to obtain a final film.

In the step (c), the longitudinal stretching is preferably longitudinally stretched at a relatively low magnification ratio of 1.05 to 1.3 times at 60 to 90 占 폚 with only one longitudinal stretching step in the longitudinal direction. If the stretching magnification of the longitudinal stretching exceeds 1.3 times, preferable data can be obtained regarding the mechanical strength in the longitudinal direction and the number of initial ruptures, but the shrinkage in the longitudinal direction tends to become large, which is not so preferable. Thereafter, the film stretched in the longitudinal direction is preferably stretched in the transverse direction under a predetermined condition. That is, it is preferable that the transverse stretching is performed so that the magnification is 3.0 to 4.5 times at 60 占 폚 to 85 占 폚 in a state in which both lateral edges of the transverse direction are held by the clip in the tenter. When the stretching temperature exceeds 85 캜, the shrinkage rate in the transverse direction tends to be lowered, the thickness irregularity tends to increase, and the voids having a large volume are hardly formed at the time of stretching, so that the apparent specific gravity of the film tends to increase, I do not. On the other hand, if the stretching temperature is lower than 60 캜, the orientation in the transverse direction becomes too high, which tends to break during the transverse stretching, which is not preferable. When the draw ratio is less than 3.0 times, it is not preferable that the film is not uniformly stretched in the transverse direction and thickness irregularity occurs. On the other hand, if the stretching magnification exceeds 4.5 times, the orientation in the transverse direction becomes too high and is liable to break at the time of stretching, which is not preferable.

The method for producing a film according to the present invention may further include a step of heat-treating the film after biaxially stretching the film. The heat treatment may be performed at 65 to 85 캜 for 5 to 30 seconds while holding both ends of the width direction in the tenter by a clip. When the heat treatment temperature is 85 DEG C or less, the heat shrinkage ratio in the transverse direction can be maintained.

Hereinafter, the present invention will be described in detail with reference to Examples and the like, but the scope of the present invention is not limited by the Examples.

Manufacturing example  One: Polyester-based  Resin and Incompatible  Amorphous adult Bridged  Production of Polymeric Resin Particles

Crosslinked polymethylmethacrylate (PMMA) beads were prepared as follows, as crosslinked polymeric resin particles which are non-compatible with the polyester resin and are non-crystalline and amorphous.

Specifically, 1 wt% of sodium lauryl sulfate (SLS) as a surfactant was added to water as a solvent, and the mixture was stirred at 70 to 80 ° C for 1 hour. Thereafter, 0.01 to 0.5% by weight of potassium persulfate as a water-soluble initiator was added and stirred again. 1 to 3% by weight of methyl methacrylate (MMA) monomer was added thereto, 1 to 2% by weight of ethylene glycol diacrylate (EGDMA) was added as a crosslinking agent, and the mixture was stirred for 3 to 4 hours. The completion of the reaction was confirmed. Then, the solvent of the reaction solution was evaporated through drying, filtered, and passed through a sieve to obtain PMMA beads having an average particle diameter of about 0.8 탆.

Example  1 to 5 and Comparative Example  1 to 4: white porosity Heat-shrinkable Polyester-based  Production of film

≪ Production of copolymerized polyester resin >

120 moles of the sum of ethylene glycol and neopentyl glycol was added to an autoclave equipped with a stirrer and a distillation tower to 100 moles of terephthalic acid as an acid component, 0.07 wt% of manganese acetate as a transesterification catalyst was added to the weight of dimethylterephthalic acid , And the reaction was allowed to proceed by removing methanol as a by-product while raising the temperature to 220 ° C.

When the transesterification reaction was completed, 0.07% by weight of silica having an average particle diameter of 0.28 탆 with respect to the weight of terephthalic acid was added, and 0.4% by weight of trimethyl phosphate as a stabilizer was added. After 5 minutes, 0.035% by weight of antimony trioxide and 0.005% by weight of tetrabutyl titanate were added as polymerization catalysts, and the mixture was stirred for 10 minutes. Then, the reactant was transferred to a second reactor equipped with a vacuum apparatus, and then the reactor was gradually reduced in pressure while being heated to 285 DEG C and polymerized for about 210 minutes to obtain a copolymer polyester resin.

≪ Preparation of polyester resin composition >

(Dupont) as the inorganic particles, polystyrene (GPPS 25SP; LG Chem) as the polymer resin, and PMMA obtained in Production Example 1 as the crosslinked polymer resin particles as the polymer particles The beads were mixed to prepare a polyester resin mixture.

division Copolymerized polyester resin (% by weight) Titanium dioxide
(weight%) polystyrene
(weight%) PMMA bead
(weight%) Example 1 85 3 10 2 Example 2 85 5 8 2 Example 3 85 5 5 5 Example 4 85 3 2 10 Example 5 85 1.5 2 11.5 Comparative Example 1 85 5 10 0 Comparative Example 2 85 3 0 12 Comparative Example 3 85 15 0 0 Comparative Example 4 85 12 3 0

≪ Production of film &

The resin mixtures of Examples 1 to 5 and Comparative Examples 1 to 4 thus prepared were melted at 280 占 폚, extruded from a T-die with a casting roll, and then cooled to obtain an unstretched film. The unstretched film was preliminarily heated on a preheating roll to a film temperature of 85 캜 and then heated to a temperature of 85 캜 and a high speed rotating roll set at a surface temperature of 30 캜 to adjust the temperature Lt; / RTI > Thereafter, the film was stretched in the transverse stretching zone in a state of holding both longitudinal sides of the film in the transverse direction by a clip, and stretched 4.0 times in the transverse direction at 80 캜.

Then, the transversely stretched film was guided to a final heat treatment zone in the tenter in a state where both ends in the width direction were gripped by a clip, heat treated at 75 DEG C for 10 seconds, cooled, and both edges were cut off, To obtain a single-layer biaxially stretched film of 40 mu m continuously.

Experimental Example  1: Characteristic evaluation of film

The heat shrinkage, apparent specific gravity, light transmittance, shrinkability, shrink finishing property and process stability of the films prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were evaluated by the following methods. The measurement results are shown in Table 2.

① Heat shrinkage

The film sample was cut into a length of 300 mm and a width of 15 mm in the direction of the shrinkage measurement, treated for 10 seconds in hot water at 80 ± 0.5 ° C, and the change in length was measured to calculate the heat shrinkage rate.

Heat shrinkage percentage (%) = ((length before shrinkage - length after shrinkage) / length before shrinkage) x 100

② Apparent specific gravity of film

And measured according to ASTM-D792.

③ Light transmittance

The measurement was carried out in accordance with ASTM-D1003 using a haze meter manufactured by Gardner BYK.

④ Siming

Seaming was carried out by applying 1,3-dioxolane to the film and sticking two sheets together. Thereafter, the film was cut into a predetermined width in the direction orthogonal to the seaming direction, and pulled out under a condition of 300 mm / min with an adhesive force tester to measure the filming property.

Good: When the force when the film is peeled is 500 gf / 30 mm or more

Bad: The force when the film is peeled is 500 gf / 30 mm or less

⑤ Contraction finishability

Both ends of the printed film were adhered with 1,3-dioxolane to prepare a cylindrical label (a label in which the main shrinking direction of the heat-shrinkable film was set in the circumferential direction). Thereafter, a shrinkage test was conducted on a 500 ml PET bottle using a steam tunnel. Thereafter, shrink finishing property was visually evaluated according to the following criteria.

○: None of wrinkles, warps, and defects occurred

△: one or both of wrinkles, warping, shortage of shrinkage

X: Wrinkles, warping and shortage of shrinkage occurred

division thickness Heat shrinkage Apparent specific gravity Light transmittance Siming Province Shrink finishing property Example 1 40 70 0.92 35.7 Good ○ Example 2 40 72 0.90 32.5 Good ○ Example 3 40 67 0.95 29.0 Good ○ Example 4 40 60 0.94 37.6 Good △ Example 5 40 71 0.90 29.7 Good ○ Comparative Example 1 40 65 1.06 41.3 Bad △ Comparative Example 2 40 45 1.11 45.7 Bad X Comparative Example 3 40 50 1.45 16.0 Good △ Comparative Example 4 40 55 1.24 21.7 Bad △

As shown in Table 2, the white porous heat shrinkage of Examples 1 to 5, which contained titanium dioxide in an amount of 1 to 10 wt% based on the total film weight, and 3 to 20 wt% of polystyrene resin and PMMA beads in total, The cast polyester film had an apparent specific gravity of less than 1.0, a heat shrinkage rate of 50 to 80%, and a light transmittance of 40% or less. In addition, the white porous heat-shrinkable polyester films of Examples 1 to 5 were found to have excellent filming properties and shrink finishing properties.

On the other hand, the white porous heat-shrinkable polyester films of Comparative Examples 1, 2, and 4, which did not contain any one of polystyrene resin and PMMA beads, had unsatisfactory filming and shrink finishing properties and had an apparent specific gravity of 1.0 or more, The films of Comparative Examples 1 and 2 in which the content of titanium was out of the range of 1 to 10 wt% had a high light transmittance and the film of Comparative Example 4 had a low light transmittance. In addition, the white porous heat-shrinkable polyester film of Comparative Example 3, which did not contain both components, was inferior in that the apparent specific gravity was increased due to the high proportion of titanium dioxide.

The results show that by including titanium dioxide, polystyrene and PMMA beads in the polyester based resin in a specific amount, a low apparent specific gravity can be achieved in addition to excellent heat shrinkage and light transmittance.

Claims (13)

(a) a polyester resin, (b) an inorganic particle, (c) a polymer resin which is incompatible with the polyester resin, and (d) a polymer resin particle which is crosslinked with the polyester resin and which is non- Including,
Wherein the content of the inorganic particles is 1 to 5 wt% based on the total weight of the film, the sum of the content of the polymer resin and the crosslinked polymer resin particles is 3 to 20 wt%
The stretching ratio in the longitudinal direction is 1.05 to 1.3, the stretching ratio in the transverse direction is 3.0 to 4.5,
An apparent specific gravity of not less than 0.7 and less than 1.0, and a transverse heat shrinkage of 50 to 80% when treated for 10 seconds in hot water of 80 ± 0.5 ° C.
The method according to claim 1,
Wherein the polyester resin is a polyester homopolymer resin, a polyester copolymer resin or a blending resin thereof.
The method according to claim 1,
Characterized in that the inorganic particles are selected from the group consisting of kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium dioxide, calcium phosphate, carbon black and mixtures thereof. film.
The method of claim 3,
The white porous heat-shrinkable polyester film according to claim 1, wherein the inorganic particles are titanium dioxide.
The method according to claim 1,
Wherein the polyester resin and the incompatible and crystalline polymer resin are selected from the group consisting of a polystyrene resin, a polyolefin resin, a polyacrylic resin, a polycarbonate resin, a polysulfone resin, a cyclic olefin resin, a cellulose resin, Lt; RTI ID = 0.0 > thermally shrinkable < / RTI > polyester film.
6. The method of claim 5,
The white porous heat-shrinkable polyester film according to claim 1, wherein the polyester resin and the incompatible and crystalline polymer resin are polystyrene resins.
The method according to claim 1,
Wherein the polyester resin and the non-compatible, non-crystalline, crosslinked polymer resin particles are selected from the group consisting of an acrylic resin, a cyclic olefin copolymer resin (COC), a polyurethane resin, an epoxy resin, a nylon resin, a silicone resin, a polypropylene resin, Methylpentene resin, a polycarbonate resin, a polyacrylonitrile resin, a copolymer resin thereof, and a mixture thereof. The white porous heat-shrinkable polyester film according to claim 1,
8. The method of claim 7,
Wherein the polyester resin and the non-compatible, non-crystalline, crosslinked polymer resin particles are crosslinked polymethyl methacrylate.
The method according to claim 1,
Wherein the polyester resin and the non-compatible, non-crystalline, crosslinked polymer resin particles have a diameter of 0.1 占 퐉 to 10 占 퐉.
The method according to claim 1,
The white porous heat-shrinkable polyester film
Wherein the polyester film is used for producing a cylindrical label having a main shrinkage direction in a circumferential direction.
The method according to claim 1,
The white porous heat-shrinkable polyester film is characterized in that the light transmittance of the white porous heat-shrinkable polyester film is 40% or less.
The method according to claim 1,
Wherein the white porous heat-shrinkable polyester film is a single layer.
The method according to claim 1,
Wherein the inorganic particles are contained in an amount of 1 to 2 wt%, the crystalline polymer resin is contained in an amount of 1.5 to 2.5 wt%, the crosslinked resin particles are contained in an amount of 12 to 14 wt% Wherein the inorganic particles have a diameter of 2 to 3 占 퐉 and the cross-linked resin particles have a diameter of 0.7 to 0.9 占 퐉.