Propane diol-based polyester resin and shrink film

The present invention relates to a shrink polymer film made of a copolymerized polyester resin having a 2-methyl-1,3-propanediol unit and a copolymerized polyester resin forming the film, and more particularly, 2-methyl-1,3-propane. The present invention relates to a copolymerized polyethylene terephthalate resin in which ethylene glycol units are replaced by diol units. The shrinkage and crystallization rate of the polymer film of the present invention can be changed by the content of 2-methyl-1,3-propanediol units.

Shrinkable films are known and are used in many applications, such as labels that fit bottles by shrinkage and other size-changeable articles. Above all, using a polyester-based shrink film in a polyester container is extremely advantageous because it can be recycled without being mixed with other incompatible resins.

When a shrink film is used for a label or the like, characters, images, etc. are usually printed. Therefore, the shrink film is preferably a film that can be printed by direct or adhesion-promoting coating or such a treatment. Further, in many applications, the shrink film is preferably a clear film or a transparent film. Furthermore, it is preferably stable under conditions such as normal packaging, transportation and storage. It is also necessary to be able to produce economically and to minimize the use of organic solvents and other environmentally problematic compounds. Further, it is preferable that the film is compatible with in-line coating. That is, a film that satisfies each of the above requirements is desired.

Known shrink films include PVC (polyvinyl chloride), stretched polystyrene films, and films such as copolymerized polyesters that are more environmentally sensitive, such as copolymerized polyethylene terephthalate (PETG) with 1,4-cyclohexanedimethanol units. Can be mentioned. These films have excellent shrinkage and good mechanical properties and appearance. However, a film that is more economical than a film made of PETG or other known resins is desired. Further, it is desirable that the film is highly recyclable and can be manufactured by slightly improving a normal PET film manufacturing apparatus.

It is known that diol-based polyester resins can be used for shrink films (see, for example, Patent Document 1). This type of polyester resin is a copolymerized polyester having a propanediol unit, but the propanediol used here does not have a simple molecular structure such as 2-methyl-1,3-propanediol. However, it is a compound having a highly branched structure such as 2-methyl, 2-ethyl-1,3-propanediol and 2-methyl, 2-propyl-1,3-propanediol. Many other propanediol compounds are known, but 2-methyl-1,3-propanediol is not known, and the use of 2-methyl-1,3-propanediol is disadvantageous. Conceivable. Further, although there is a suggestion of a copolymerized polyester having a propanediol unit as described above, a shrink film made of a copolymerized polyester having a propanediol unit is not actually manufactured or sold, and a copolymer having a propanediol unit is not manufactured or sold. There may be technical limitations and other difficulties in the production of the intended shrink film using polyester.

<patcit num="1"><text>U.S. Pat. No. 4,962,291</text></patcit>

<p> An object of the present invention is to provide a shrinkable polyester film having excellent shrinkage.</p><p> Another object of the present invention is to provide a shrinkage polyester film whose shrinkage properties can be easily controlled.</p><p> Another object of the present invention is to provide a shrinkage polyester film which is economical in its production.</p><p> Another object of the present invention is to provide a shrinkage polyester film in which crystallization occurs slowly.</p>

<p> Polyesters having 1,3-propanediol units are known to be prone to crystallization. Similarly, polymers with 1,3-propanediol units can be added as materials to promote crystallization. Such a property seems to be a material that is not suitable for increasing the shrinkage rate of the shrink film. However, 1,3-propanediol substituted with the carbon at the 2-position of 1,3-propanediol rather delays crystallization. That is, it is considered that the shrinkage rate can be increased by containing such a substituted 1,3-propanediol unit.</p><p> The present inventors have found that a film having excellent shrinkage properties can be obtained by partially substituting the ethylene glycol component in polyethylene terephthalate with 2-methyl-1,3-propanediol. That is, it contains a propanediol unit having a smaller number of branched structures than the propanediol-based copolymerized polyester, which has been conventionally suggested to be applied to shrinkage films, but was believed not to obtain satisfactory shrinkage. The above properties have been found in a film using a copolymerized polyester. Then, they have found that a film using a copolymerized polyester using 2-methyl-1,3-propanediol has a shrinkage property superior to that of a known shrinkage film. Further, while the component used in the known shrink film has a structure having a benzene ring, the 2-methyl-1,3-propanediol component found in the present invention has a linear structure having a methyl group. Have.</p><p> Therefore, it has been found that the above object can be achieved by partially replacing the ethylene glycol component in polyethylene terephthalate with 2-methyl-1,3-propanediol. That is, it was found that the shrinkage characteristics and crystallinity of the film can be controlled by changing the content of 2-methyl-1,3-propanediol in the resin and the film.</p><p> The gist of the present invention is<u style="single">A method for producing a shrink polymer film made of a copolymerized polyester resin. The dicarboxylic acid component of the copolymerized polyester resin is terephthalic acid, and the diol component is composed of ethylene glycol and 2-methyl-1,3-propanediol. The composition ratio of 2-methyl-1,3-propanediol units in the components is more than 10 mol% and 35 mol% or less, and shrinkage in the main shrinkage direction when treated in a hot water bath at 80 ° C for 10 seconds. The ratio is 50 to 80%, and the production method comprises a step of extruding the copolymerized polyester resin and a step of stretching so that the stretching ratio in the main stretching direction is 2 to 10 in at least one direction. A method for producing a shrinkable polymer film, which comprises not performing heat treatment after the stretching step.</u>Exists in.</p>

<p> The shrinkable polymer film of the present invention has excellent shrinkage characteristics, the shrinkage characteristics and crystallinity can be easily controlled, and the production thereof is excellent in economy.</p>

Hereinafter, the present invention will be described in detail. The propanediol used in the present invention is 2-methyl-1,3-propanediol, which is a mono-substituted propanediol. As 2-methyl-1,3-propanediol, "MP" manufactured by Lyondell Chemical Company "Diol" is preferable because it is available as a commercial product. Copolymerized polyesters with 2-methyl-1,3-propanediol units have a glass transition temperature (Tg) that allows film production. If the copolymerized polyester has a Tg that is too low to be sticky at room temperature, it will be difficult to apply in many applications. Copolymerized polyesters using propanediol, which has more branched structures than 2-methyl-1,3-propanediol, have a lower Tg. Such polyesters are difficult to produce (polymerize) and have adhesiveness, making them unsuitable as polymers. In addition, shrink films using such polymers may cause unintended shrinkage due to sudden temperature rises that occur during storage and transportation, and can be provided as commercial products to end users and consumers. Absent. However, in such a case, the desired contraction characteristics cannot be achieved in the first place. In the present invention, the glass transition temperature (Tg) of the above-mentioned copolymerized polyester is preferably 50 to 72 ° C, more preferably 55 to 65 ° C, and particularly preferably 60 to 63 ° C.

Copolymerized polyesters having 2-methyl-1,3-propanediol units have a glass transition temperature (Tg) high enough to solve the above problems, and 2-methyl-1,3-propanediol units. It has a high glass transition temperature (Tg) even if its content is relatively high. For example, a copolymerized polyester having a content of 2-methyl-1,3-propanediol units of 35 mol% is non-crystalline and completely amorphous. In the case of a copolymerized polyester having a diol unit having a structure with many branches as described above in the same content, the copolymerized polyester is completely amorphous but has the above-mentioned problems and is not applicable.

Films made of copolymerized polyesters containing 2-methyl-1,3-propanediol units have excellent heat-sealing properties, and at normal heat-sealing temperatures, not only heat-seal between films, but also other materials. Heat sealing can also be performed on the surface of. As a heat sealing condition, heat sealing is performed at a temperature of 90 to 170 ° C for 0.5 to 10 seconds. The conditions adopted in the heat seal test of the present invention are a temperature of 90 ° C and a pressure of 40 pounds / inch.²<u style="single">(28000kg / m</u>^{<u style="single">2</u>}<u style="single">)</u>For 5 seconds. Heat seal pressure is 20-60 psi during the above heat seal time<u style="single">(14000 ~ 42000kg / m</u>^{<u style="single">2</u>}<u style="single">)</u>(Typically 40psi<u style="single">(28000kg / m</u>^{<u style="single">2</u>}<u style="single">)</u>), And may be carried out at the above-mentioned heat-sealing temperature, or only pressure may be applied instead of heating to the above-mentioned heat-sealing temperature. The heat seal test is usually performed between polymer films, but may be performed between films having a coating layer. As a test method, the force required for the seal portion to peel off or the force required for the vicinity of the seal portion to be broken is measured and evaluated. In such tests, typically 3 mils (3/1000 inches)<u style="single">(76.2 μm)</u>) Thickness film is used. And 4 lbs / inch²<u style="single">(28000kg / m</u>^{<u style="single">2</u>}<u style="single">)</u>Load the pressure of.

The 2-methyl-1,3-propanediol unit is introduced in the production of polyester by partially substituting ethylene glycol with 2-methyl-1,3-propanediol. Usually, the diol component of the polyester resin is 100 mol% of ethylene glycol units. In the present invention, the copolymerized polyester resin having a content of 2-methyl-1,3-propanediol units lower than the content of the addition unit generally used for imparting shrinkage causes higher shrinkage. I found that sex can be obtained. The content of 2-methyl-1,3-propanediol units in the diol component is 5 to 50 mol%, preferably 10 to 35 mol%, and more preferably 20 to 30 mol%. Examples of the diol constituent unit other than the 2-methyl-1,3-propanediol unit include an ethylene glycol unit, a unit other than ethylene glycol, or a combination of these units.

When the content of 2-methyl-1,3-propanediol units (that is, the amount of substitution with ethylene glycol units) exceeds 10 mol%, amorphousness increases and shrinkage due to reheating increases. Here, high contractility means a case where the contraction rate in the main contraction direction exceeds 50%. The shrinkage rate is measured in a hot water bath at 80 ° C (or 99 ° C in some cases) for 10 seconds. That is, the length is measured in all directions of the sample and immersed in a hot water bath for 10 seconds. Then, the length of the sample after the treatment is measured, and the shrinkage rate is determined as compared with that before the treatment.

The content of 2-methyl-1,3-propanediol units can be up to 100 mol%. However, under normal polymerization conditions, the reaction rate of 2-methyl-1,3-propanediol is 44 to 45 mol%, and it is difficult to obtain a molecular weight sufficient for use. However, copolymerized polyesters containing 2-methyl-1,3-propanediol units are less susceptible than other more highly branched copolymerized polyesters containing propanediol units. That is, in a copolymerized polyester containing a more highly branched propanediol unit, the above-mentioned problems occur unless the content of the propanediol unit is limited to a low level. Then, even if the content of the propanediol unit is slightly changed, the shrinkage characteristics are greatly changed, and it becomes difficult to formulate the shrinkage characteristics, manufacture and control the film. However, in a copolymerized polyester containing 2-methyl-1,3-propanediol units, the shrinkage characteristics change more slowly even if the content of 2-methyl-1,3-propanediol units is changed. , A degree of freedom can be obtained in the formulation and manufacture of shrinkage properties.

A method for producing a base film is described in US Pat. No. 5,350,601 (written by Culbertson et al.), Which is incorporated herein by reference. Diol and / or glycol components and dicarboxylic acid components (or esters thereof) such as terephthalic acid, isophthalic acid, sebacic acid, malonic acid, adipic acid, azelaic acid, glutaric acid, suberic acid, succinic acid or a mixture of two or more thereof. It is preferably produced by a polycondensation reaction with a derivative). Preferred glycols include polyols such as ethylene glycol, diethylene glycol, polyethylene glycol and butanediol, and these may be used in combination of two or more.

Films with a shrinkage of less than 50% are used in some areas where low shrinkage is required, especially for polyester films. However, films having a shrinkage ratio of more than 50% have been conventionally preferred in the market, especially in the market such as packaging label films. In the embodiment of the present invention, the preferred shrinkage rate in the main shrinkage direction is 50 to 80% (assuming maximum shrinkage), more preferably 60 to 80%, still more preferably 70 to 80%, and particularly preferably 75 to 80. %.

By using the preferred resin in the present invention, technical merits can be obtained. For example, a resin having a 2-methyl-1,3-propanediol unit has a lower viscosity than a constituent resin of a PETG-based shrink film obtained as a commercially available product. Therefore, a resin film having 2-methyl-1,3-propanediol units can be produced by using a device for producing a normal polyester resin film with only a slight change. Further, the low viscosity has the technical effect of reducing the generation of heat due to shear stress, making the filter last longer, and reducing the formation of streaks and streaks in the film.

The film of the present invention can contain known additives. Additives include pigments, other colorants, stabilizers (including, but not limited to, UV stabilizers), antistatic agents, adhesion promoters, antioxidants, matting agents, fillers, plasticizers, lubricants. And so on.

The shrinkage film of the present invention can change the content of 2-methyl-1,3-propanediol units in a wide range. Thereby, for example, a film having a shrinkage rate of 78% in the main shrinkage direction and a film having a shrinkage temperature of more than 80 ° C can be obtained. A known film having a small shrinkage rate can also be produced. Being able to flexibly handle the production of such a wide variety of films has the advantage of being adaptable to a wide variety of production lines. In the film of the present invention, it is preferable that the maximum shrinkage rate can be achieved at less than 80 ° C., whereby the processing speed of the film can be increased and the film can be processed at a low temperature in the shrinkage step. .. Films with a content of 0 mol% of 2-methyl-1,3-propanediol units (ie PET films) are essentially non-shrinkable. A film with a content of 2-methyl-1,3-propanediol units of 35 mol% returns to almost 100% the size of the film before lateral stretching due to heat shrinkage.

Since the film of the present invention has high amorphous property, the tensile strength is increased and the film is excellent in impact resistance. Furthermore, since 2-methyl-1,3-propanediol is cheaper than other available propanediols, the film of the present invention can be produced cheaper than known shrink films. In addition, despite the relatively low content of 2-methyl-1,3-propanediol, it exhibits excellent shrinkage properties. Therefore, the film of the present invention can be produced at a lower cost than a known film in which a larger amount of a diol component that contributes to shrinkage or another component that imparts shrinkage must be used.

The polyester constituting the polyester film of the present invention is preferably made by polycondensing terephthalic acid and its equivalents of 2-methyl-1,3-propanediol and ethylene glycol. The optimum copolymer is preferably prepared from 100 mol% terephthalic acid, an amount of 2-methyl-1,3-propanediol capable of achieving the desired shrinkage, and the remaining amount of ethylene glycol.

The shrinkable polyester resin constituting the polyester film of the present invention is used alone or as a main component in the polyester film. As a preferred embodiment, a blend of the polyester resin of the present invention and another polyester resin and / or a resin other than polyester can be used. By using such a blend, the content of 2-methyl-1,3-propanediol can be easily adjusted. For example, by blending an equal amount of a copolymerized polyester having a content of 2-methyl-1,3-propanediol unit of 35 mol% and a polyester containing no 2-methyl-1,3-propanediol unit in equal amounts. , The content of 2-methyl-1,3-propanediol units can be adjusted to 17.5 mol%. The properties of the resulting film can also be adjusted by blending PETG, PEN, polystyrene and various other resins.

The film of the present invention is highly transparent and does not have stripes. That is, such properties are important when applied to many packaging films, as the contents and other packaging materials can be seen through the film.

The film of the present invention can have a known coating layer. The coating layer is not particularly limited, and examples thereof include an adhesion promoting layer, a surface modification layer, a printing adhesion promoting layer, an antistatic layer, a blocking resistant layer, a matte layer, a heat seal layer, and a gas barrier layer. The coating liquid is preferably aqueous in consideration of dissolution of the film surface by the solvent of the coating liquid, environmental problems, safety in manufacturing work, and the like.

The thickness of the film of the present invention can take a wide range depending on the application. When used for labels and other applications, the film thickness is preferably 10 to 200 μm, more preferably 25 to 100 μm.

The physical characteristics of the film having the recycled raw material are important when the scrap film having the coating layer is mixed with the new raw material and recycled, except when the film is excessively yellowed or the physical properties are deteriorated. By being able to reuse the waste film, it is possible to save raw materials, reduce disposal costs, and reduce unnecessary waste. The film of the present invention has excellent reusability properties.

Further, the film of the present invention can be a laminated body. The laminates include polymer / polymer laminates such as polyester / polyolefin laminates, polyester / adhesive / polyolefin laminates, polymer / metal laminates such as polyester / aluminum laminates, polymer / paper laminates, and polymers / adhesives. / Paper laminate etc. can be mentioned. A polymer film having a coating layer and a film laminate can also be used for the above laminate. In order to improve the wettability of the film surface and the adhesiveness of the coating layer, providing an adhesive layer is also included in the coating layer.

The film of the present invention can be produced by a known method. For example, the polyester resin is melted and extruded onto a mirror rotating drum to form an amorphous sheet. The resulting sheet is quenched and stretched in one or more directions to impart film strength, toughness and desired shrinkage. Usually, the amorphous sheet is stretched 2 to 10 times, preferably 4 to 7 times in one or more directions. Uniaxial stretching is preferable to biaxial stretching. And stretching in the lateral direction is preferable.

The stretching temperature is usually a temperature between the secondary transition temperature of the polymer and the softening / melting point of the polymer. If necessary, after stretching, the film is heat-treated (heat-fixed) by annealing to fix the properties of the film. In particular, it is effective when the content of 2-methyl-1,3-propanediol unit is low and it has semi-crystallinity, or when 2-methyl-1,3-propanediol is added as a modifier. By heat treatment, dimensional stability and good tensile properties can be imparted. The heat treatment is usually carried out at a temperature of 190 to 240 ° C. Such a heat treatment temperature is preferable when the content of 2-methyl-1,3-propanediol units is high. When the content of 2-methyl-1,3-propanediol units is low, the heat treatment temperature is preferably 80 to 100 ° C. In the present invention, when producing a film having a high shrinkage rate, heat treatment does not have to be performed.

No particular surface modification of the polymer film is required, but it is preferable to modify the surface of the polymer film before forming a coating layer that imparts the desired properties. As a known surface modification method, corona treatment is the most common and preferable, and it is possible to impart adhesiveness to the coating layer to the film surface. Corona treatment or other surface modification methods should be used to ensure sufficient wettability with the coating liquid when the coating layer is provided. For that, it is usually about 1.0 W / (feet)² Minutes<u style="single">(10.76W / m</u>^{<u style="single">2</u>}<u style="single"> Minutes)</u>It is preferable to carry out the corona treatment with the strength of. Further, an adhesive layer or another intermediate layer may be optionally provided between the polymer film and the above-mentioned coating layer.

Example 1, Comparative Examples 1 to 3: Using the copolymerized PET resin shown in Table 1 below, a film stretched uniaxially 5 times was prepared. The obtained film was heated using a hot air gun and the shrinkage rate was measured. Heating was performed at 80 ° C and 99 ° C. The film of Example 1 having 2-methyl-1,3-propanediol units has a higher shrinkage rate, particularly a heating temperature of 80, as compared with the films of Comparative Examples 1 to 3 having other copolymerized diol units. The effect was remarkable at ° C.

<tables num="1"><img file="JP4782002B2_D0001.tif" /></tables>

Although the present invention has been described above in relation to embodiments that are both practical and preferred, the present invention is not limited to the embodiments disclosed in the present specification, and claims are made. It can be appropriately changed as long as it does not contradict the gist or idea of the invention that can be read from the scope and the entire specification, and it must be understood that the technical scope of the present invention is accompanied by such a change.