JP2009084486A - New polyester and polyester composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester and a polyester composition, excellent in gas barrier property without requiring complex production steps at a low cost, and to provide films and packaging materials comprising the polyester or the polyester composition. <P>SOLUTION: The polyester has an ester constituent unit comprising dihydroxyacetone and a dicarboxylic acid. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to polyesters and polyester compositions. More specifically, the present invention relates to a polyester having an ester structural unit composed of a diol and a dicarboxylic acid.

  Polyester, for example, polyethylene terephthalate (hereinafter referred to as “PET”) has excellent mechanical strength, thermal characteristics, chemical stability, transparency and the like, and is excellent in production cost. Widely used in films, food packaging materials, etc. In particular, when used as a food packaging material, high gas barrier performance is required from the viewpoint of the spread of preserved foods and the diversification of packaging forms. However, since PET has insufficient gas barrier properties against oxygen and carbon dioxide, its use in applications that require high gas barrier performance such as food packaging materials and carbonated beverage containers that require long-term storage is still limited. Therefore, further improvement in gas barrier properties is demanded.

As a method of improving the gas barrier property of PET, a method of substituting a part or all of the terephthalic acid component of PET with isophthalic acid or naphthalenedicarboxylic acid (Patent Documents 1 and 2), other resins having a high gas barrier property such as poly A method of laminating or mixing vinylidene chloride, polyvinyl alcohol, polyamide, polyglycolic acid or the like (Patent Documents 3 and 4), a method of depositing aluminum or silicon (Patent Documents 5 and 6), and the like have been proposed.
JP 2004-292647 A JP 2005-239797 A JP 2003-136657 A JP 2004-285194 A JP-A-6-278240 Japanese Patent Laid-Open No. 11-10725

  However, each method has problems such as a complicated manufacturing process and high cost, and the gas barrier property is still not sufficiently satisfactory.

  Accordingly, an object of the present invention is to provide a polyester and a polyester composition that do not require a complicated production process, are low in cost, and have excellent gas barrier properties. Another object of the present invention is to provide a film and a packaging material containing the polyester and the polyester composition of the present invention.

  As a result of intensive studies to obtain a polyester having excellent gas barrier properties, the present inventor has improved gas barrier properties compared to conventional PET when formed into a film by using polyester having dihydroxyacetone as a monomer unit. As a result, the present invention has been completed.

  That is, the present invention is a polyester having an ester structural unit (A) composed of dihydroxyacetone and dicarboxylic acid.

  Moreover, this invention provides the polyester composition containing said polyester (a) and other polyester (b).

  Furthermore, the present invention provides a film or packaging material comprising the polyester or polyester composition described above.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the polyester and polyester composition excellent in gas barrier property at low cost without requiring a complicated manufacturing process. Furthermore, according to the polyester and the polyester composition of the present invention, it is possible to provide a film and a packaging material that are suitably used as containers and packaging materials for beverages and foods.

  The present invention is a polyester having an ester structural unit (A) composed of dihydroxyacetone and dicarboxylic acid. In the present invention, the “ester structural unit” means a repeating unit of an alternating copolymer containing an ester bond obtained by polycondensation of a diol and a dicarboxylic acid.

  In the polyester of the present invention, the dicarboxylic acid constituting the ester structural unit (A) together with dihydroxyacetone is not particularly limited as long as it can form an ester bond by polycondensation with dihydroxyacetone. , Isophthalic acid, phthalic acid, 2,6-, 1,5-, 1,6-, 1,7-, or 2,7-naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, biphenyl ether dicarboxylic acid, biphenyl sulfone dicarboxylic acid, Aromatic dicarboxylic acids such as benzophenone dicarboxylic acid, phenylindane dicarboxylic acid, metal salt of 5-sulfoxyisophthalic acid, phosphonium salt of 5-sulfoxyisophthalic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid , Suberic acid, azelain , Sebacic acid, fumaric acid, and aliphatic dicarboxylic acids such as cyclohexane dicarboxylic acid. These dicarboxylic acids may be used alone or in combination of two or more. Among them, at least one kind selected from terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid is preferable in that a polyester having excellent gas barrier properties and mechanical properties is obtained, and terephthalic acid is more preferable. preferable.

  Here, as a preferable form of said ester structural unit (A), the unit shown by a following formula is mentioned, for example.

R ₁ in the formula is a p-phenylene group, m-phenylene group, o-phenylene group, 2,6-naphthyl group, ethylene group, propylene group, or butylene group. In the polyester of the present invention, one or more R ₁ may be contained. From the viewpoint of obtaining a polyester excellent in gas barrier properties, R ₁ is a p-phenylene group, an m-phenylene group, or 2,6. -A naphthyl group is preferable, and a p-phenylene group is more preferable. In the case of including a plurality of R _{1 s} , the arrangement of each ester structural unit may be random or block-like.

  The polyester of the present invention is characterized by having the above-mentioned ester structural unit (A) as an ester structural unit, and further comprises an ester structural unit (B) comprising a diol other than dihydroxyacetone and a dicarboxylic acid. Can have. By including different structural units in the polymer chain in this way, it is possible to control properties such as gas barrier properties, moldability, and mechanical strength of the resulting polyester.

  As dicarboxylic acid used for formation of ester structural unit (B), the same thing as dicarboxylic acid used for formation of structural unit (A) may be used, and a different thing may be used. The dicarboxylic acids listed above can also be suitably used. Moreover, these dicarboxylic acids may use only 1 type, or may contain 2 or more types. Among these, from the viewpoint of obtaining a polyester having excellent transparency, at least one selected from terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid is preferably used, and terephthalic acid is more preferably used.

  Moreover, there is no restriction | limiting in particular as diol used for formation of the ester structural unit (B) which can be contained, Specifically, ethylene glycol, propylene glycol, 1,3-propanediol, 2,2-dimethyl -1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,6- Xanthdiol, thiodiethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, diethylene glycol, triethylene glycol or tetraethylene A glycol etc. can be mentioned. As the diol, at least one of these can be used, but the main component is most preferably ethylene glycol. Further, the diol component is used in an amount that is substantially equivalent to the dicarboxylic acid component described above.

  As a preferable form of said ester structural unit (B), the unit shown by a following formula is mentioned, for example.

In the formula, R ₂ is an ethylene group, a propylene group, or a butylene group, and R ₃ is a p-phenylene group, an m-phenylene group, an o-phenylene group, a 2,6-naphthyl group, an ethylene group, a propylene group, or It is a butylene group, preferably R ₂ is an ethylene group, and R ₃ is a p-phenylene group.

  Moreover, it is preferable that content of ester structural unit (A) is 10-100 mol% with respect to all the ester structural units, as for the polyester of this invention, it is more preferable that it is 30-100 mol%, 50-100 mol% It is particularly preferred. By setting the content of the ester structural unit (A) with respect to all the ester structural units to 10 mol% or more, a polyester having improved gas barrier properties can be obtained.

  Furthermore, the polyester of the present invention may be used by blending with other polymers. Other polymers to be blended are not particularly limited as long as they do not impair the object of the present invention, and examples thereof include polyolefins, polyesters, and polyamides. Among these, they are mixed with other polyesters in that they are uniformly mixed. Blends are preferred. That is, another preferred embodiment of the present invention may be a polyester composition containing a polyester (a) having an ester structural unit (A) composed of dihydroxyacetone and a dicarboxylic acid and another polyester (b).

  Examples of the polyester (b) that can be added include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, polyethylene 2,6 naphthalate, polytrimethylene 2,6 naphthalate, polybutylene 2,6 naphthalate, poly Hexamethylene 2,6 naphthalate, polyethylene isophthalate, polytrimethylene isophthalate, polybutylene isophthalate, polyhexamethylene isophthalate, poly 1,4 cyclohexane dimethanol terephthalate aromatic polyester, polylactic acid, polycaprolactone, polybutylene Aliphatic polyesters such as succinate, polyethylene adipate, and polybutylene adipate are listed. Among these, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene 2,6 naphthalate are preferable, and polyethylene terephthalate is more preferable. Moreover, the polyester (b) added may be only 1 type in the said polyester, or may contain 2 or more types.

  The weight ratio of the polyester (a) and the polyester (b) is not particularly limited as long as the object of the present invention is not impaired. From the viewpoint of gas barrier properties, the content of the polyester (a) is the total amount of the polyester composition. On the other hand, it is preferably 10% by weight or more and less than 100% by weight, more preferably 30% by weight or more and less than 100% by weight, and particularly preferably 50% by weight or more and less than 100% by weight.

<Manufacturing method>
The polyester in the present invention is characterized by containing the above-mentioned ester structural unit as a structural unit, but the production method is not particularly limited, and is produced by a conventionally known method similar to PET. be able to.

  Examples of the production method include a method (direct polymerization method) in which a dicarboxylic acid and a diol are directly esterified. That is, a diol such as dihydroxyacetone and a dicarboxylic acid such as terephthalic acid are preferably esterified by distilling off water at a pressure of 150 to 280 ° C. or at normal pressure, and then performing polycondensation under reduced pressure. Thereby, the polyester which has the ester structural unit of the hydroxyacetone-carboxylic acid of this invention is obtained. The above esterification reaction may be performed without adding any catalyst, or may be performed in the presence of an acid such as concentrated sulfuric acid or p-toluenesulfonic acid, or a catalyst such as a metal complex, but is preferably performed without a catalyst. .

  In general, the direct polymerization method requires a lot of heat energy. Furthermore, when polymerization is performed at a high temperature, the polymer may cause thermal decomposition, and it may be difficult to obtain a high molecular weight aliphatic polyester by a direct polymerization method.

  Other production methods include mixing and reacting an ester-forming derivative of a carboxylic acid and a diol component, distilling off lower alcohols such as hydrogen halide and methyl alcohol to be produced, and esterifying or transesterifying, An example is a method in which the obtained reaction product is further polycondensed under reduced pressure. Here, as ester-forming derivatives of carboxylic acids, dicarboxylic acids such as acid halides, acid anhydrides and the like that have high reaction activities and promote esterification reactions, dicarboxylic acids and alcohols, Derivatives that are esters with ethylene glycol or the like and that generate esters by esterification or transesterification are mentioned.

  For example, polyhydroxyacetone terephthalate, which is a polyester of dihydroxyacetone and terephthalic acid, can be produced by mixing and esterifying an acid chloride of terephthalic acid such as terephthalic acid dichloride and dihydroxyacetone.

  Polycondensation by transesterification is usually performed by melt polymerization, but melt polymerization and solid phase polymerization may be used in combination. The solid phase polymerization is carried out by converting the polyester obtained by melt polymerization into pellets or powders, and holding the polyester at a temperature below the melting point of the polyester under reduced pressure or in an inert gas atmosphere. When solid state polymerization is performed, polyester having a high intrinsic viscosity and high molecular weight can be obtained, and the mechanical strength of the polyester can be improved.

  In the above transesterification reaction and polycondensation reaction, the reaction temperature, pressure, etc. may be determined in accordance with a conventionally known polyester polymerization method.

  Further, no catalyst may be added in the reaction, and a catalyst and / or a stabilizer may be used. As the transesterification catalyst, one or more known compounds such as calcium, manganese, zinc, magnesium, cobalt, sodium and lithium compounds can be used, but magnesium and manganese compounds are preferable from the viewpoint of transparency. As the polycondensation catalyst, one or more kinds of known antimony, germanium, titanium, cobalt compounds and the like can be used. What is necessary is just to select said manufacturing method suitably according to manufacturing cost or desired molecular weight.

  Although the manufacturing method in particular of the polyester composition of this invention is not restrict | limited, For example, it can manufacture by melt-mixing the polyester of this invention obtained by said method, and another polyester. What is necessary is just to perform melt mixing according to the melt mixing method of a conventionally well-known polyester composition. Examples of the apparatus for performing the melt mixing include a single screw extruder, a twin screw extruder, a plast mill, a kneader, various extrusion molding machines and injection molding machines, or a reactor equipped with a stirring device and a decompression device.

  Alternatively, solid phase polymerization may be further performed after melt mixing. Solid-phase polymerization may be carried out according to a conventionally known method, and can be carried out by holding the molten mixture at a temperature below its melting point under reduced pressure or in an inert gas atmosphere. Since the molecular weight of the polyester contained in the polyester composition is increased by solid phase polymerization and a polyester composition having improved mechanical strength is obtained, it is preferable.

<Use for film and packaging materials>
The polyester of the present invention thus obtained can be used for films, sheets, containers, and other packaging materials using injection molding methods, blow molding methods, uniaxial stretching methods, biaxial stretching methods and the like commonly used in PET. Can be molded.

  Films and packaging materials obtained by molding the polyester of the present invention by these methods are materials excellent in gas barrier properties against oxygen, nitrogen and carbon dioxide.

  In general, when the molecular chains are oriented by stretching rather than in a random state, the gap between the molecular chains is smaller and gas is less permeable, so the polyester of the present invention is stretched at least in a uniaxial direction. Furthermore, gas barrier properties and mechanical strength can be improved.

  Furthermore, the polyester of the present invention may be molded into a form laminated with another polyester.

<Gas barrier properties>
In general, the gas barrier property of a polymer is said to have a great influence on the free volume representing the gap between polymer molecular chains, the cohesiveness of the polymer molecular chains, the strength of the interaction between the gas molecules and the polymer constituent units, and so on. .

  As a method for easily estimating the permeability of gas molecules to a polymer, a gas permeability estimation method based on a quantitative structure property relationship (QSPR) is known. This method uses a bond index obtained from graph theory to estimate physical properties such as a permeability coefficient of the polymer from the chemical structure of the polymer (Bicerrano, J. Prediction of Polymer Properties, Third Edition, Marcel Decker Inc.). , New York, 2002).

  The Material Studio (R) Ver4.1 Synthia module from Accelrys Software, Inc. can estimate the gas permeability of the polymer using the method described above. Specifically, the structural unit of the polymer and its repeating structure are defined using Visual Studio's 3-D sketcher of Material Studio (registered trademark) Ver 4.1 manufactured by Accelrys Software, Inc, and the gas for these polymers is defined by the Synthia module. Estimate permeation properties of molecules. The permeation properties at room temperature (298 K) of oxygen, nitrogen, and carbon dioxide for the two polymers shown in Table 1 were estimated by the above method. Table 2 shows the results.

  The smaller the value of the permeability coefficient, the better the gas barrier property. From the above estimation results, the polyester (PHAT) of dihydroxyacetone and terephthalic acid according to the present invention has an oxygen permeability coefficient of 0.30 times, a nitrogen permeability coefficient of 0.27 times, and dioxide dioxide compared to ordinary PET. The carbon permeability coefficient is 0.27 times, and it can be confirmed that PHAT has better gas barrier properties than PET.

Claims (13)

  A polyester having an ester structural unit (A) composed of dihydroxyacetone and dicarboxylic acid. The polyester according to claim 1, wherein the ester structural unit (A) is represented by the following formula:

In the formula, R ₁ is a p-phenylene group, m-phenylene group, o-phenylene group, 2,6-naphthyl group, ethylene group, propylene group, or butylene group. The polyester according to claim 2, wherein R ₁ is a p-phenylene group.   The polyester according to any one of claims 1 to 3, further comprising an ester structural unit (B) composed of a diol other than dihydroxyacetone and a dicarboxylic acid. The polyester according to claim 4, wherein the ester structural unit (B) is represented by the following formula:

In the formula, R ₂ is an ethylene group, a propylene group, or a butylene group, and R ₃ is a p-phenylene group, an m-phenylene group, an o-phenylene group, a 2,6-naphthyl group, an ethylene group, a propylene group, or It is a butylene group. The polyester according to claim 5, wherein R ₃ is a p-phenylene group. The polyester according to claim 5 or 6, wherein R ₂ is an ethylene group.   The polyester according to any one of claims 1 to 7, wherein the content of the ester structural unit (A) is 10 to 100 mol% with respect to all ester structural units.   A polyester composition containing the polyester (a) according to any one of claims 1 to 8 and another polyester (b).   The polyester composition according to claim 9, wherein the polyester (b) is polyethylene terephthalate.   The polyester composition according to claim 9 or 10, wherein the content of the polyester (a) is 10% by weight or more and less than 100% by weight with respect to the total amount of the polyester composition.   The film containing the polyester of any one of Claims 1-8, or the polyester composition of any one of Claims 9-11.   The packaging material containing the polyester of any one of Claims 1-8, or the polyester composition of any one of Claims 9-11.