JPH0770303A - Thermally shrinkable polyester film - Google Patents

Abstract

PURPOSE:To obtain the title film having high slipperiness and transparency. CONSTITUTION:The film is made from polyester resin obtd. by reacting a dicarboxylic acid component with a diol component mainly comprising ethylene glycol and contains 50-350ppm inorg. particles together with internal particles contg. calcium and phosphorus in such amts. that the calcium content in the film is 250-450ppm and the wt. ratio of phosphorus to calcium is 0.6-1.2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polyester film, and more specifically, it has excellent heat-shrinkability, good slipperiness, and high transparency.
The present invention relates to a heat-shrinkable polyester film used for various packaging materials and the like.

[0002]

2. Description of the Related Art Heat-shrinkable polyester film is used as a part of containers, fishing rods, condensers, indications on rod-shaped fluorescent lamps, protection of contents, bundling, and addition of value to products. In addition to being used, it is widely used for the purpose of packing and tightly packing books and notebooks. At present, in addition to this, in various fields, development of various applications utilizing the shrinkage characteristics of the film is progressing.

Conventionally, resins such as polyvinyl chloride, polystyrene, and polyolefin have been mainly used as resins for heat-shrinkable films. However, since such resins and the like have drawbacks in practical use in terms of heat resistance, weather resistance, chemical resistance, etc., there has been no choice but to limit the range of use thereof. For example, a polyvinyl chloride film can be processed into a heat-shrinkable film having various shrinkage characteristics, but fish eyes are liable to occur frequently, and it is possible to obtain sufficient commercial value without impairing aesthetics especially in printing applications. Can not. Furthermore, as a major problem, polyvinyl chloride film causes chlorine-based gas at the time of incineration to corrode the incinerator, and when such chlorine-based gas is released into the atmosphere, it causes acid rain, especially in forest resources. Various reports have been made that it causes great damage. In addition, since such a resin contains a large amount of plasticizer, dust is likely to adhere to the bleed-out plasticizer and stains occur, which easily causes a defect in terms of safety.

On the other hand, a heat-shrinkable film obtained from polystyrene has a good finished appearance after shrinkage, but it has low solvent resistance and requires the use of a special ink during printing. Because of contraction, it has to be stored in a cool place. Further, it is necessary to incinerate at a high temperature, and a large amount of black smoke and an offensive odor are generated at the time of incineration. A polyester film as a film that solves these problems is highly expected, and the amount of its use is increasing remarkably.

However, the polyester film has poor slipperiness due to its resin characteristics, and defective winding shape occurs as the process line speed is increased, resulting in problems such as process troubles and quality defects in products. ing. Further, when used as a heat-shrinkable label for bottles, etc., the decrease in the slipperiness of the film causes shrinkage unevenness due to friction with the bottle etc. in the shrinking process by heat treatment after the film is wrapped around the bottle, etc. The result is unaesthetic.

As one of the solutions to the problem, there is a method of reducing dynamic friction by adding a pigment typified by titanium oxide. Although such a method is generally adopted as an external particle method, although such a method can greatly improve the slip property of the film, on the other hand, haze increases, and transparency required as a heat shrinkable film for packaging materials is particularly high. Tend to be impaired. In addition, the external particles have poor adhesiveness to the resin and are likely to fall off during the process and during use, and satisfactory performance has not yet been obtained.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted earnest research on a heat-shrinkable polyester film which does not impair the heat-shrinkable property and transparency and has a slip property practically sufficient. I arrived. That is, the present invention is
A film comprising a polyester resin containing (A) a dicarboxylic acid component containing an aromatic dicarboxylic acid or an ester-forming derivative thereof as a main component and (B) a diol component containing an ethylene glycol as a main component, The content of calcium element in the film is 250-450pp
m, an internal particle having a phosphorus element content of 0.6 to 1.2 in terms of element amount ratio to calcium element, and 50 to 350 p
A heat-shrinkable polyester film containing inorganic particles of pm.

A feature of the present invention is that the external particle method and the internal particle method are used together as a means for imparting slipperiness, so that sufficient slipperiness and transparency are simultaneously satisfied. That is, the internal particle method is used as a method of suppressing the haze increase, which is a drawback of the external particle method.

In the internal particle method, when a polyester is produced, a metal compound used as an esterification catalyst for the polyester and a phosphorus compound used for suppressing thermal decomposition at the time of polymerization are reacted in a condensation reaction process to produce a metal phosphate. Fine particles having a salt as a nucleus are formed, and these particles have the property of improving the slipperiness of the film surface. Particles produced by the internal particle method have very good adhesiveness with the resin unlike the external particles, and during the process, not only the drop during use is small, but the haze is extremely low even if sufficient slipperiness is expressed, It can have an almost transparent appearance.

The present invention is characterized in that the internal particles are formed such that the contents of the calcium element and the phosphorus element are the specified amounts. Calcium forming the internal particles is added to the reaction system as a calcium compound, and as the compound used in this case, hydroxide, oxide, carbonate,
Examples thereof include inorganic substances such as hydrogen carbonate and organic acid salts such as acetate, propionate, butyrate and stearate, and one or more of these compounds can be used in combination.

Calcium added as a calcium compound reacts with phosphorus to form nuclei of internal particles, so that the slipperiness of the film improves as the content of calcium element increases, but on the other hand, calcium is a polymer. Addition of an excessive amount is not preferable because it also promotes thermal decomposition of Further, when the internal particles have a large particle size distribution and are produced in a large amount, they also cause filter clogging in the film forming step, so that the content of the calcium element contained in the film is 250 to 450 ppm. Add a calcium compound so that. This is because when the content of the calcium element is less than 250 ppm, the amount of internal particles to be precipitated is small and sufficient slipperiness cannot be obtained, and when it exceeds 450 ppm, the particle amount tends to be large and the particle size tends to increase. Therefore, the filtration pressure is increased and the process passability becomes poor.

Further, elemental phosphorus is added to the reaction system as a phosphorus compound, and examples of the phosphorus compound include phosphoric acid, phosphorous acid or their esterified products such as trimethyl phosphate, triethyl phosphate, triphosphate. Phenyl, triethyl phosphite, triphenyl phosphite and the like can be mentioned, and one or more of these compounds can be used in combination.

The amount of phosphorus compound added is preferably determined based on the amount of calcium element. This is because the internal particles are formed through the reaction between phosphorus and calcium, so it is not necessary to add more than a certain amount to the amount of elemental calcium, and excessive phosphorus is added to calcium. In this case, excess phosphorus also reacts with the polymerization catalyst, reducing the catalytic ability, and a polyester having a high degree of polymerization cannot be obtained. Further, when the amount of phosphorus is less than a certain amount with respect to calcium, the result is that phosphorus and unreacted calcium accelerate thermal decomposition of the polymer. Therefore, the phosphorus element content needs to be in the range of 0.6 to 1.2 in terms of the element amount ratio of the phosphorus element to the calcium element.

While the internal particles have the above-mentioned excellent properties, they have low particle strength and are small in size as compared with inorganic particles such as silica, so that they are good when the pressure applied when sliding the film is small. However, when the applied pressure is high, the slipperiness is lowered and a sufficient effect cannot be obtained. In order to make up for such drawbacks, in the present invention, a small amount of inorganic particles is used in combination with the internal particles. Examples of the inorganic particles used include silica, calcium carbonate, titanium dioxide, calcium phosphate, and the like.
The type is not particularly limited, but silica particles having a good affinity with polyester are particularly preferable from the viewpoint of maintaining transparency and preventing the film from falling off from the film surface.

As the silica particles used in the present invention, those having a refractive index close to that of polyester are preferable, and in order to prevent the particles from falling off the film surface, amorphous silica having a high affinity with polyester is preferable. Also,
Silica particles are added in the range of 50 to 350 ppm, preferably 100 to 300 ppm. this is,
This is because if the silica particles are less than 50 ppm, sufficient slipperiness cannot be obtained, and if the silica particles exceed 350 ppm, the transparency of the film is lowered due to the formation of coarse particles.
In addition, it is preferable that the particle size of the silica particles is such that the temporary particles have a particle size of 20 μm or less and the particle size is 5 to 50 μm, preferably 10 to 30 μm in the film.

The polyester resin used in the heat-shrinkable polyester film of the present invention contains terephthalic acid or its ester-forming derivative as a main component as a dicarboxylic acid component, and ethylene glycol, butanediol, cyclohexanedimethanol and a bisphenol compound as a diol component. The main component is one or more selected from ethylene oxide adducts of its derivatives, and it may be a specific one or more polyester resins alone or a mixture of two or more different polyester resins. Examples of the ester-forming derivative of terephthalic acid include dialkyl ester and diaryl ester of terephthalic acid.

In the present invention, the dicarboxylic acid component constituting the polyester resin has terephthalic acid or its ester-forming derivative as a main component, and is contained in an amount of 60 mol% or more in all dicarboxylic acid components of the polyester resin. It is more preferably 70 mol% or more. In the present invention, other aromatic dicarboxylic acid such as isophthalic acid, naphthalene-1,4- or -2,6-dicarboxylic acid is used for the purpose of increasing the amount of heat shrinkage at low temperature or improving solvent adhesion. The aliphatic dicarboxylic acid or its ester-forming derivative may be contained in the total dicarboxylic acid component in an amount of less than 40 mol%, preferably less than 30 mol%. This is because these dicarboxylic acid components are 4
This is because if the content is 0 mol% or more, the mechanical strength of the polyester film may decrease. Examples of the aliphatic dicarboxylic acid that can be used in the present invention include glutaric acid, adipic acid, sebacic acid, oxalic acid and succinic acid.

In the present invention, the diol component constituting the polyester resin contains at least one selected from ethylene glycol, butanediol, cyclohexanedimethanol and an ethylene oxide adduct of a bisphenol compound or its derivative as a main component. However, it is preferable that these diol components are contained in an amount of 80 mol% or more in all the diol components.

In the present invention, the diol component is particularly preferably one containing ethylene glycol as a main component. Furthermore, an ethylene oxide adduct of a bisphenol compound or derivative is added to all diol components in an amount of 0.1 to 0.1%.
A content of 50 mol%, preferably 0.5 to 30 mol% is preferable from the viewpoint of shrinkage characteristics and shrinkage unevenness at low temperatures. This is because if the content of the ethylene oxide adduct of bisphenol A is less than 0.1 mol%, the effect of reducing shrinkage unevenness is small, and if it exceeds 50 mol%, the shrinkage characteristics at low temperatures deteriorate. Examples of the ethylene oxide adduct of the bisphenol compound or its derivative include those having the structures represented by the following general formulas (I) and (II).

[0020]

[Chemical 1]

[0021]

[Chemical 2]

Among them, an ethylene oxide adduct of bisphenol A having the structure of the following general formula (III) is preferable.

[0023]

[Chemical 3]

In addition, it is preferable to contain polyoxytetramethylene glycol and / or polyethylene glycol as the diol component, because they are more effective in improving the low temperature shrinkability and reducing the shrinkage unevenness.
The polyoxytetramethylene glycol or polyethylene glycol is contained in the resin in an amount of 0.01 to 30% by weight, preferably 0.01 to 20% by weight.
Is the range.

This has a polyoxytetramethylene glycol or polyethylene glycol content of 0.01.
If it is less than 10% by weight, there is no sufficient effect for improving the low-temperature shrinkability or reduction of shrinkage unevenness. This is because it causes deterioration of mechanical strength and mechanical strength. The polyoxytetramethylene glycol that can be used in the present invention preferably has an average molecular weight of 300 to 4000, more preferably 500 to 3000. The polyethylene glycol preferably has an average molecular weight of 300 to 20,000, more preferably 1,000 to 20,000. This is because if the average molecular weight is less than the above, the effect of reducing shrinkage unevenness or improving the low temperature shrinkability is small, and if the average molecular weight is more than the above average, the compatibility with the resin tends to be poor.

Further, in the present invention, other diol components such as propylene glycol, triethylene glycol, diethylene glycol and neopentyl glycol are added,
It can also be used in a range that does not impair the effects of the present invention, for example, in a range of 20 mol% or less.

Further, in the present invention, a polyhydric carboxylic acid having a valence of 3 or more and / or a polyhydric alcohol is added to each of the acid component or the alcohol component in order to suppress abrupt shrinkage and generate any shrinkage behavior. It can also be used in the range of 0.01 to 1 mol%. This is because a range below this range is insufficient for controlling the shrinkage behavior, and a range above this range may cause gelation during polymerization. Examples of the trivalent or higher polycarboxylic acid and polyhydric alcohol include polycarboxylic acids such as trimellitic acid, pyromet acid and their anhydrides, and polyhydric alcohols such as trimethylolpropane, pentaerythritol and glycerin. Among these, trimethylolpropane, trimellitic acid, and pentaerythritol are preferable from the viewpoints of thermal stability during film formation and reactivity during polycondensation.

The heat shrinkage rate of the heat shrinkable polyester film of the present invention is preferably 20% or more at 60 ° C. in one direction (shrinking direction) when heated for 60 seconds in a hot water bath. This is because if the shrinkage ratio at 60 ° C. is less than 20%, the adhesion of the film to the container will not be sufficient,
This is because the heating temperature in the shrinking process must be raised. This is because if the heating temperature in the shrinking step is increased, the container such as a bottle is deformed or whitened, and the heat-shrinkable film is rapidly shrunk, which causes uneven shrinkage. More preferably, the shrinkage percentage at 60 ° C. is 25% or more.

The polyester resin used in the present invention can be produced by a known direct polymerization method, transesterification method or the like, and the degree of polymerization thereof is not particularly limited,
Intrinsic viscosity (measured in a mixture of phenol / tetrachloroethane in a weight mixture at 25 ° C) due to the moldability of the original film
Is preferably about 0.5 to 1.2 dl / g.

The obtained polyester resin is molded into a heat-shrinkable polyester film by the following method, for example. First, the polyester resin is dried, melted, melt-extruded from a die, and a raw film is formed by a casting method, a calendering method, or the like. Then, this raw film was set to 3 from the glass transition temperature (Tg) of the polyester resin.
1.5 to 5.0 times in the longitudinal or transverse direction, preferably 1.0 at a temperature higher than ℃, preferably higher than 5 ℃
The film is stretched to 4.8 times to give a high shrinkage rate to the film. Further, if necessary, 1.0 in the direction perpendicular to the stretching direction.
To 1.8, preferably 1.0 to 1.5 times. This is effective in improving the mechanical strength of the film and preventing excessive shrinkage in the stretching direction.

The film is stretched by simultaneous biaxial stretching and sequential 2
It is carried out by a method such as axial stretching or uniaxial stretching, and either longitudinal stretching or lateral stretching may be performed first. The stretched heat-shrinkable polyester film can be used as a product as it is, but may be heat-treated at a temperature of 50 ° C. to 150 ° C. for several seconds to several tens seconds from the viewpoint of dimensional stability and the like. By carrying out such heat treatment, preferable properties such as adjustment of the shrinkage ratio in the shrinking direction of the polyester film of the present invention, reduction of time-dependent shrinkage during storage of the unshrinked film, reduction of shrinkage unevenness, etc. can be exhibited.

The thickness of the heat-shrinkable polyester film of the present invention is not particularly limited, but is 1 to 600 μm.
Those in the range of are practically used. 6 to 380 μm for packaging applications, especially packaging of foods, beverages, pharmaceuticals, etc.
Those in the range of are used. Also, 20 to 70μ for PET bottles, polyethylene bottles, and glass bottle labels.
Those in the range of m are used.

The heat-shrinkable polyester film of the present invention may be subjected to various conventionally known processing treatments in order to impart further specific performance thereto, or may be blended with suitable additives. Examples of processing include ultraviolet rays, α rays, β
Examples include irradiation with rays, γ rays or electron beams, corona treatment, plasma irradiation treatment, flame treatment and the like, application of resin such as vinylidene chloride, polyvinyl alcohol, polyamide and polyolefin, lamination, and metal deposition. Examples of additives include polyamide, polyolefin, polymethylmethacrylate, resins such as polycarbonate, talc, inorganic particles such as kaolin, ultraviolet absorbers,
Examples include a release agent and a twisting agent.

The present invention will be specifically described below with reference to Examples and Comparative Examples. Evaluations in Examples and Comparative Examples were performed by the following methods.

1. Haze (%) Tokyo Denshoku Co., Ltd. haze meter (MODEL TC-
HIII) to measure the haze of the film.

2. Dynamic friction coefficient Using a surface tester manufactured by Shinto Kagaku Co., Ltd., the same film was attached to both the fixed part and the movable part to measure the dynamic friction coefficient.

3. Thermal shrinkage 150 mm in the drawing direction and 20 mm in the direction perpendicular to the drawing, on a polyester film cut out, the marked lines are spaced 1
The length between the marked lines before contraction (L) and the length between the marked lines after contraction (L ' ) Was measured and it calculated | required by the following formula.

Shrinkage rate (%) = {(L−L ′) / L} × 100

4. Shrinkage unevenness When a polyester film cut out to a size of 150 mm in the stretching direction and 20 mm in the perpendicular direction is heat-shrinked in warm water of 60 ° C for 60 seconds without load, occurrence of shrinkage unevenness in the film, and a container Occurrence of looseness of the film when the film was shrunk by coating was visually evaluated according to the following three grades. ◯: Almost no shrinkage unevenness was observed, and no loosening occurred even when the coating was easily shrunk. Δ: Some shrinkage unevenness occurred, and some looseness occurred when the coating was easily shrunk. : Significant shrinkage unevenness and significant loosening when the container is covered and shrunk

The abbreviations in Table 1 indicate the following compounds. TPA: terephthalic acid IPA: isophthalic acid ADA: adipic acid SA: sebacic acid EG: ethylene glycol NPG: neopentyl glycol BPAE: bisphenol A ethylene oxide adduct TMP: trimethylolpropane PTMG: polyoxytetramethylene glycol (molecular weight 2000)

[0041]

【Example】

Example 1 82 mol parts of terephthalic acid, 11.5 mol parts of isophthalic acid, 6.5 mol parts of adipic acid, 10 ethylene glycols
0 parts by mole, 40 parts by mole of bisphenol A ethylene oxide adduct (m + n = 1) represented by the general formula (III),
After 0.2 parts by weight of polytetramethylene glycol was placed in a reaction vessel for esterification, a 2% by weight solution of calcium acetate monohydrate in ethylene glycol was used as a calcium element in an amount of 300 ppm, and an ethylene glycol solution of trimethyl phosphate was treated with phosphorus. 250 ppm as an element, 30 amorphous silica (Fuji Devius, Syroid # 150)
After adding to the reaction system so as to be 0 ppm, polymerization was carried out by a direct polymerization method to obtain a resin for the heat-shrinkable polyester film of the present invention. After drying this resin, it was melt extruded at 270 ° C. to prepare a raw film film. This film stock is 70
Uniaxially stretched 4 times in the transverse direction at ℃, thickness is 12μm
To obtain a heat-shrinkable polyester film. The composition of the obtained film is shown in Table 1, and the evaluation results are shown in Table 2.

Examples 2 to 4 and Comparative Examples 1 to 4 In Example 1, the calcium content, phosphorus content and amorphous silica content were changed as shown in Table 1, and Example 1 was changed.
The above method was repeated to obtain a heat-shrinkable polyester film having a thickness of 12 μm. The evaluation results of the obtained film are shown in Table 2.

Example 5 82 mol parts of terephthalic acid, 11.5 mol parts of isophthalic acid, 6.5 mol parts of adipic acid, 14 ethylene glycol
After 0 mol part was placed in a reaction vessel for esterification, a 2 wt% ethylene glycol solution of calcium acetate monohydrate was used as a calcium element at 300 ppm, and an ethylene glycol solution of trimethyl phosphate was used as a phosphorus element at 250 ppm.
ppm and amorphous silica (Cyroid # 150 manufactured by Fuji Devius Co., Ltd.) were added to the reaction system so that the concentration would be 300 ppm, followed by direct polymerization to obtain a resin for the heat-shrinkable polyester film of the present invention. After drying this resin 2
Melt extrusion was performed at 70 ° C. to prepare a raw film film. This raw material film was uniaxially stretched 4 times in the transverse direction at 70 ° C. to obtain a heat-shrinkable polyester film having a thickness of 12 μm. The composition of the obtained film is shown in Table 1, and the evaluation results are shown in Table 2.

Example 6 82 mol parts of terephthalic acid, 15 mol parts of isophthalic acid, 3 mol parts of sebacic acid and 140 mol parts of ethylene glycol were placed in a reaction vessel for esterification, and then 2 parts of calcium acetate monohydrate was added. A weight% ethylene glycol solution is 300 ppm as a calcium element, an ethylene glycol solution of trimethyl phosphate is 250 ppm as a phosphorus element, and amorphous silica (Fuji Devius Syroid # 150).
Was added to the reaction system so as to be 300 ppm, followed by direct polymerization to obtain a resin for the heat-shrinkable polyester film of the present invention. After drying this resin, it was melt extruded at 270 ° C. to prepare a raw film film. This raw film is uniaxially stretched 4 times in the transverse direction at 70 ° C to obtain a thickness of 1
A 2 μm heat-shrinkable polyester film was obtained. The composition of the obtained film is shown in Table 1, and the evaluation results are shown in Table 2.

Example 7 100 parts by mole of terephthalic acid and 120 of ethylene glycol
After 30 parts by mole of neopentyl glycol and 30 parts by mole of neopentyl glycol were placed in a reaction vessel for esterification, a 2 wt% ethylene glycol solution of calcium acetate monohydrate was added as a calcium element at 300 ppm, and an ethylene glycol solution of trimethyl phosphate was added as phosphorus. 250 ppm as an element, 300 amorphous silica (Fuji Devius Syroid # 150)
After adding to the reaction system so as to be ppm, polymerization was carried out by a direct polymerization method to obtain a resin for the heat-shrinkable polyester film of the present invention. After drying this resin, it was melt extruded at 270 ° C. to prepare a raw film film. This film stock is 70
Uniaxially stretched 4 times in the transverse direction at ℃, thickness is 12μm
Table 1 shows the composition of the obtained film, and Table 2 shows the evaluation results.

Example 8 75 mol parts of terephthalic acid, 25 mol parts of isophthalic acid, 150 mol parts of ethylene glycol, 5 mol parts of bisphenol A ethylene oxide adduct (n + m = 2), polyoxytetramethylene glycol (molecular weight 1000) 1.
After 5 mol parts and 0.15 mol parts of trimethylolpropane were placed in a reaction vessel for esterification, a 2 wt% ethylene glycol solution of calcium acetate monohydrate was added as calcium element at 300 ppm, and trimethyl phosphate of ethylene glycol was added. The solution was added to the reaction system as a phosphorus element with a concentration of 250 ppm and amorphous silica (Cyroid # 150 manufactured by Fuji Devius Co., Ltd.) to a concentration of 300 ppm, followed by direct polymerization to polymerize the resin for the heat-shrinkable polyester film of the present invention. Got After drying this resin, it was melt extruded at 270 ° C. to prepare a raw film film. This raw film was uniaxially stretched 4 times in the transverse direction at 70 ° C. to obtain a thickness of 12
A μm heat-shrinkable polyester film was obtained. The composition of the obtained film is shown in Table 1, and the evaluation results are shown in Table 2.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

As described above, the heat-shrinkable polyester film of the present invention has excellent shrinkage properties, high transparency and practically sufficient slipperiness by combining the constitution as described above. It is useful for various packaging materials.

Claims (1)

[Claims] 1. A dicarboxylic acid component containing (A) an aromatic dicarboxylic acid or an ester-forming derivative thereof as a main component,
(B) A film made of a polyester resin containing ethylene glycol as a main component and a diol component as a main component, wherein the content of calcium element is 2
A heat-shrinkable polyester film containing 50 to 450 ppm, internal particles having a phosphorus element content of 0.6 to 1.2 in terms of element amount ratio to calcium element, and 50 to 350 ppm of inorganic particles.