KR19990079802A - Polytrimethylene terephthalate film and its manufacturing method - Google Patents

Abstract

The present invention comprises a polytrimethylene terephthalate resin and inert particles having an average particle size in the range of 0.5 to 2.5 μm, based on the weight of the resin, from 0.05 to 0.50 wt%, with one side or both sides being polyvinyridine chloride. The present invention relates to a biaxially oriented polytrimethylene terephthalate film and a method for manufacturing the same, wherein the film is coated with a thickness of 2 to 6 μm, and the film according to the present invention has excellent flex-crack resistance and gas barrier property. It can be usefully used as a food packaging material.

Description

Polytrimethylene terephthalate film and its manufacturing method

Polytrimethylene terephthalate (PTT) is a type of crystalline polyester with the following general formula:

Here, when m is 2, it is polyethylene terephthalate (PET),

When m is 3, it is polytrimethylene terephthalate (PTT),

When m is 4, it is polybutylene terephthalate (PBT).

As a plastic material, polytrimethylene terephthalate contains properties of polyethylene terephthalate, polybutylene terephthalate and nylon, and has suitable properties for fibers, films, plastic containers, engineering plastics, etc., except that it has the lowest melting point. As a rule, they have intermediate properties between polyethylene terephthalate and polybutylene terephthalate. That is, polytrimethylene terephthalate exhibits the same excellent strength, stiffness and impact strength as polyethylene terephthalate, and has excellent low temperature meltability, molding temperature, crystallization rate, etc., such as polybutylene terephthalate. It is also a very good polymer in terms of dimensional stability, electrical insulation and chemical resistance, which are basic properties of aromatic polyester. In addition, the polytrimethylene terephthalate film has excellent abrasion resistance, toughness, and the like as in nylon.

The three aromatic polyesters mentioned above, that is, polyethylene terephthalate, polytrimethylene terephthalate and polybutylene terephthalate, are characterized by very different characteristics due to the difference in the number of methyl groups included in the repeating unit. In particular, since the difference in crystallization characteristics affecting the molding process of the crystalline polymer and the characteristics of the molded article is very large, there is a difference in each molding method and use. Polyethylene terephthalate has the lowest crystallization rate among the three polymers, and is therefore easier to manufacture a transparent container by blow molding and fiber, film or sheet use and blow molding than injection molding. Polybutylene terephthalate has a very high crystallization rate, making it difficult to form a film by sequential biaxial stretching like polyethylene terephthalate, while it is possible to shorten the production cycle and to produce an injection-molded article. The polytrimethylene terephthalate has a crystallization rate in the middle of the two polymers, but its characteristics are very specific, so that the injection conditions or the film stretching process may be performed under conditions of forming the polyethylene terephthalate or polybutylene terephthalate. Is very different. In particular, the molding conditions of conventional polyethylene terephthalate are very different in molding into a successive biaxially oriented film. In addition, the amorphous sheet of polytrimethylene terephthalate has a drawback that the drawing conditions are very difficult because the crystallization proceeds more rapidly than the polybutylene terephthalate at the stretching temperature.

Flex-crack resistance, on the other hand, is a very important property in food packaging, especially in the packaging of natural or processed cheese. In the case of cheese slice packaging, if pinholes occur during long-term distribution channels or during the handling of consumers, the cheese is damaged by contact with oxygen. In addition, long-term distribution or storage requires gas and water vapor barriers such as oxygen. The characteristics required for the packaging of cheese are different depending on the type of cheese. In all cases, excellent flex-crack resistance is required. In the case of natural cheese, oxygen permeability is 0.6cc / 100in ² ㆍ 24hr. It should be less than atm and less than 0.5g / 100in ² ㆍ 24hr · atm water vapor permeability. In the case of processed cheese, since it is pasteurized, oxygen barrier property of 1cc / 100in ² · 24hr · atm or less which is somewhat lower than natural cheese is required.

Conventional packaging films, such as nylon films, are excellent in flex-crack resistance properties and gas barrier properties but are highly hygroscopic, which is undesirable. In the case of polyethylene terephthalate films, oxygen barrier properties can be obtained when gas barrier coatings are made of a material such as polyvinylidene chloride, but the required level of flex-crack resistance properties cannot be obtained.

Accordingly, an object of the present invention is to provide a biaxially oriented polytrimethylene terephthalate film having excellent flex-crack resistance and gas barrier properties by eliminating the above disadvantages and coating the surface with an appropriate lubricant.

Another object of the present invention is to provide a method for producing the biaxially orientated polytrimethylene terephthalate film.

In order to achieve the above object, the present invention comprises a polytrimethylene terephthalate resin and inert particles having an average particle diameter in the range of 0.5 to 2.5㎛ of 0.05 to 0.50% by weight based on the weight of the resin, It provides a biaxially oriented polytrimethylene terephthalate film, characterized in that both sides are coated with a thickness of 2 to 6 ㎛ with polyvinylidene chloride.

In addition, in the present invention, a polytrimethylene terephthalate mixed resin containing 0.05 to 0.50% by weight of inert particles is melt-extruded under a temperature condition of 275 to 290 ° C to prepare a sheet, and the sheet is in a temperature range of 45 to 75 ° C. Longitudinally stretched at 1.5 to 3.5 times at a temperature of 1.5 to 3.5 times in a temperature range of 50 to 85 ° C., heat-set at a temperature of 120 to 180 ° C., and quenching at a temperature of 25 to 40 ° C. to prepare a biaxially oriented film. Then, it provides a method for producing a biaxially oriented polytrimethylene terephthalate film, characterized in that one or both sides of the film is coated with a polyvinylidene chloride in a thickness of 2 to 6㎛.

Hereinafter, the present invention will be described in detail.

The polytrimethylene terephthalate resin used in the present invention can be prepared by condensation polymerization of 1,3-propanediol (1,3-PDO) and terephthalic acid (TPA) or dimethyl terephthalate (DMT) after transesterification.

In addition, the polytrimethylene terephthalate film of the present invention contains inert particles having an average particle diameter of 0.5 to 2.5 µm in an amount of 0.05 to 0.50% by weight based on the weight of the polytrimethylene terephthalate resin. If the average particle diameter is less than 0.5 μm or less than 0.05% by weight, the role as a lubricant is not sufficient, so the friction coefficient becomes too large, which is not preferable because of poor processing processability. In addition, the flex-crack resistance of which the average particle diameter exceeds 2.5 µm or exceeds 0.50% by weight becomes poor, which is not preferable. More preferably, the lubricant having an average particle diameter in the range of 0.5 to 1.5 μm is added in the range of 0.05 to 0.30 wt%.

Examples of inert particles that can be used in the present invention include silica, calcium carbonate, alumina, zinc oxide and the like, with silica, calcium carbonate and alumina being particularly preferred. The lubricant of the present invention is preferably added immediately after the transesterification reaction after the transesterification reaction.

The lubricant-containing polytrimethylene terephthalate mixed resin prepared as described above is melt-extruded at a temperature condition of 275 to 290 ° C to prepare a sheet. The sheet is longitudinally stretched 1.5 to 3.5 times using hot air in the range of 45 to 75 degrees Celsius between the stretching rolls of 15 to 20 degrees Celsius in the chamber, and stretched 1.5 to 3.5 times in a tenter in the temperature range of 50 to 85 degrees Celsius. . Subsequently, heat setting may be performed at a temperature of 120 to 180 ° C., and the film may be quenched at a temperature of 25 to 40 ° C. to prepare a biaxially oriented film.

The intrinsic viscosity of the final stretched film is required to be 0.95 to 1.40 g / kPa. If the intrinsic viscosity is lower than 0.95 g / kPa, the desired flex-crack resistance property cannot be obtained. It is not preferable because it increases the production cost without improving the crack resistance characteristics. It is more preferable that the intrinsic viscosity of a film is 1.10-1.35 g / dl.

Subsequently, one side or both sides of the prepared biaxially oriented film is coated with a thickness of 2 to 6 μm polyvinylidene chloride. When coating at a thickness of less than 2㎛ can not obtain the desired gas barrier properties, coating at a thickness of more than 6㎛ can not only obtain a further effect but also increase the production cost.

Polyvinylidene chloride may be dissolved in tetrahydrofuran, methyl ethyl ketone, toluene or a mixed solvent at a concentration of 10 to 20% by weight, and then coated on a film using a separate coater.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited only to the following examples. Various performance evaluations of the films produced in Examples and Comparative Examples of the present invention were carried out by the following method:

(1) Flex-Crack Resistance Characteristics

The film sample is cut into 29x21 cm (width x length), rolled into a cylindrical shape, mounted on a Gelbo Flex (Boston Gear), a flex-crack resistance measuring device, and repeated 6000 times of twisting reciprocation. When measured, the number of pinholes generated per 100 in ² film area was measured.

(2) ultimate viscosity

After the sample was dissolved in o-chlorophenol at 100 ° C, the intrinsic viscosity was measured at 30 ° C using a Ubbelohde viscosity tube.

(3) coefficient of friction

The static / dynamic friction coefficient between films and films was measured using a Haydon type surface tester of Shindong Science Co., Ltd.

(4) gas barrier properties

It measured using ASTM D-1434 MC-1 of Toyo Seiki. At this time, the permeation area was 7 cm in diameter, the permeation pressure of oxygen was 2.0 kg / cm 2, and the permeation pressure of water vapor was 1.0 kg / cm 2.

Example 1

800 parts of dimethyl terephthalate and 595 parts of 1,3-propanediol were introduced into a transesterification reactor. When the temperature of the reactants reached about 150 ℃, tributylene titanate as a catalyst was added in an amount of 0.05% by weight based on the weight of dimethyl terephthalate, and gradually raised for 120 minutes to undergo a transesterification reaction at 220 ℃ Finished. Subsequently, 0.25 wt% of silica having an average particle diameter of 1.52 μm was added based on the weight of dimethyl terephthalate, and after about 5 minutes, 0.037 wt% of dimethyl phosphate was added as a stabilizer based on the weight of dimethyl terephthalate, and trimethylene terephthalate was added. Obtained. After about 15 minutes, antimony triacetate was added as a polymerization catalyst, and the temperature was gradually raised to 250 ° C.

The monomer thus obtained was dropped into the polymerization reactor while being pressurized with nitrogen. In the polymerization reactor, while gradually applying a vacuum, when the constant power level reached the stirrer motor, the polymerization reaction was stopped to obtain polytrimethylene terephthalate as a pellet.

The obtained polytrimethylene terephthalate resin pellets were dried in a vacuum at 150 ° C. for about 5 hours, melt-extruded to a temperature of about 283 ° C., and then quenched in a quench roll having a surface temperature of about 15 ° C. to be stretched and amorphous. The sheet was prepared. The sheet was stretched 2.5 times in the longitudinal direction at 60 ° C., stretched 3.0 times in the transverse direction using a tenter at 70 ° C., then heat set at a temperature of about 180 ° C., and cooled at a temperature of about 35 ° C. after heat setting. To give a film having a thickness of 25 μm.

The performance of the film thus prepared was evaluated and shown in Table 1. As shown in Table 1, the film prepared in Example 1 was excellent in intrinsic viscosity, flex resistance characteristics and coefficient of friction.

Examples 2-4

A biaxially oriented polytrimethylene terephthalate film of the present invention was prepared in the same manner as in Example 1 except that the average particle diameter and the concentration of silica were changed as shown in Table 1.

The performance of the film thus prepared was evaluated and shown in Table 1. As shown in Table 1, the films prepared according to Examples 2 to 4 were excellent in intrinsic viscosity, flex resistance characteristics and coefficient of friction.

Comparative Examples 1 to 5

A biaxially oriented polytrimethylene terephthalate film was prepared in the same manner as in Example 1 except for changing the average particle diameter and the concentration of silica as shown in Table 1.

The performance of the film thus prepared was evaluated and shown in Table 1. As shown in Table 1, the films prepared by Comparative Examples 1 to 5 had poor intrinsic viscosity, flex resistance characteristics and coefficient of friction.

Lubricant (SiO ₂ ) Characteristic evaluation Particle diameter density Extreme viscosity Flex-Crack Resistance Friction Coefficient (Dynamic / positive) Μm weight% g / ㎗ - - Example 1 1.52 0.25 1.28 2-3 0.36 / 0.37 Example 2 2.40 0.15 1.11 0 to 4 0.38 / 0.42 Example 3 0.73 0.25 1.34 0 to 3 0.56 / 0.58 Example 4 2.40 0.15 1.40 2 to 5 0.39 / 0.43 Comparative Example 1 0.30 0.06 1.25 2 to 4 0.75 / 0.79 Comparative Example 2 2.40 0.70 1.27 6-10 0.34 / 0.40 Comparative Example 3 2.40 0.03 1.23 3 to 5 0.59 / 0.62 Comparative Example 4 2.40 0.15 0.91 7-14 0.41 / 0.42 Comparative Example 5 2.81 0.06 0.93 Not measurable 0.46 / 0.46

Example 5

Polyvinylidene chloride was dissolved in tetrahydrofuran at a concentration of 15% by weight, and then applied to the 25 μm thick film obtained in Example 1 with a thickness of 2.5 μm using a coating machine.

To evaluate the oxygen barrier properties and water vapor barrier properties of the coated film as described above are shown in Table 2 below. As shown in Table 2, the film prepared in Example 5 was excellent in oxygen barrier property and water vapor barrier property.

Examples 6 and 7

The polyvinyridine chloride coating thickness was carried out in the same manner as in Example 5 except for changing the thickness as shown in Table 2.

To evaluate the oxygen barrier properties and water vapor barrier properties of the coated film as described above are shown in Table 2 below. As shown in Table 2, the films prepared in Examples 6 and 7 were excellent in oxygen barrier properties and water vapor barrier properties.

Comparative Example 6

Oxygen barrier properties and water vapor barrier properties of the film obtained in Example 1 without polyvinylidene chloride coating were evaluated, and the results are shown in Table 2 below. As shown in Table 2, the film of Comparative Example 6, which was not coated, had poor oxygen barrier properties and water vapor barrier properties.

Comparative Example 7

The same procedure as in Example 5 was conducted except that the thickness of the polyvinylidene chloride coating was 1.5 μm.

To evaluate the oxygen barrier properties and water vapor barrier properties of the coated film as described above are shown in Table 2 below. As shown in Table 2, the film produced by Comparative Example 7 had poor oxygen barrier properties and water vapor barrier properties.

Coating thickness Oxygen barrier Water vapor barrier Μm cc / 100in ² ㆍ 24hr g / 100in ² ㆍ 24hr Example 5 2.5 0.6 0.5 Example 6 3.1 0.4 0.5 Example 7 5.8 0.4 0.4 Comparative Example 6 - 9.3 2.8 Comparative Example 7 1.5 2.2 2.1

As described above, the polytrimethylene terephthalate film of the present invention has excellent flex-crack resistance, oxygen and water vapor barrier properties, and can be widely used as a food packaging material.

Claims (5)

Polytrimethylene terephthalate resin and inert particles having an average particle size ranging from 0.5 to 2.5 μm, based on the weight of the resin, from 0.05 to 0.50 wt%, with 2 or 6 polyvinylidene chloride on one or both sides Biaxially oriented polytrimethylene terephthalate film, characterized in that the coating is a thickness of. The method of claim 1, And said inert particles are selected from the group consisting of silica, calcium carbonate, alumina and zinc oxide. The method of claim 1, Intrinsic viscosity is 0.95-1.40g / dl, The film characterized by the above-mentioned. A polytrimethylene terephthalate mixed resin containing 0.05 to 0.50% by weight of inert particles was prepared by melt extrusion at a temperature of 275 to 290 ° C., and the sheet was 1.5 to 3.5 times at a temperature in the range of 45 to 75 ° C. After stretching in the longitudinal direction, stretching at a temperature of 1.5 to 3.5 times in the temperature range of 50 to 85 ℃, heat-setting at a temperature of 120 to 180 ℃, and quenched at a temperature of 25 to 40 ℃ to prepare a biaxially oriented film of the film A method for producing a biaxially orientated polytrimethylene terephthalate film, characterized in that one or both surfaces are coated with a thickness of 2 to 6 µm with polyvinylidene chloride. The method of claim 4, wherein And wherein said inert particles are selected from the group consisting of silica, calcium carbonate, alumina and zinc oxide.