JP6300266B2 - Copolyester resin and its hollow container - Google Patents

Description

  The present invention relates to a copolyester resin having excellent extrusion blow moldability, particularly high melt tension of the molten resin at the time of direct blow molding, little drawdown, good appearance transparency, and good color tone. The present invention relates to a hollow container formed using a resin.

  Currently, polyvinyl chloride, polyethylene terephthalate, and the like are generally used as materials for forming plastic containers with good transparency by blow molding. Polyvinyl chloride can be easily blow-molded to obtain a container in the same manner as polyethylene. Polyethylene terephthalate, on the other hand, has been increasingly used due to its mechanical strength, chemical stability, and safety as its resin properties, and is widely used as packaging material for various sheets and containers, especially carbonated drinks, fruit juice drinks, Growth as a container for liquor and wine is remarkable. In the case of polyethylene terephthalate, it is common to use a molding method in which the parison is once molded by injection molding, and then the parison is heated to a temperature above the glass transition point and stretch blow molded. The number of applications that are used in an increased manner is also increasing. The direct blow method is a method in which a parison (or preform) molded by an extrusion molding machine or an injection molding machine is still soft and does not lose its plasticity, thereby completing blow molding.

  The use of polyvinyl chloride is decreasing due to the generation of toxic gases during incineration. Polyethylene terephthalate is extremely suitable as a material for transparent hollow containers in terms of mechanical properties, gas barrier properties, safety, hygiene, etc. , The parison during extrusion is drawn down and it is difficult to mold into a hollow container itself, and crystallization is likely to occur at the time of stretch blow, resulting in a problem that transparency is impaired, and obtaining a uniform transparent container It was difficult.

  In order to solve these problems, it has been proposed to use a resin obtained by copolymerizing polyethylene terephthalate with other monomer components. Examples thereof include polyethylene terephthalate obtained by copolymerizing 1,4-cyclohexanedimethanol. However, although the introduction of these comonomers can suppress crystallization, it cannot increase the melt viscosity alone. Therefore, it is necessary to increase the degree of polymerization to a high molecular weight to increase the melt viscosity. It is possible to increase the degree of polymerization by applying solid-phase polymerization, but because the polymerization rate is low, a resin with high melt viscosity cannot be efficiently produced, and extrusion blow molding can be performed from a resin that can be produced industrially This is limited to small hollow containers.

  Accordingly, an object of the present invention is to overcome the disadvantages of the conventional polyethylene terephthalate or polyethylene terephthalate copolymer, and to produce an extrusion blow molded article having good transparency and excellent color tone with good moldability. It is to provide a polyethylene terephthalate copolymer polyester resin that can be used, and to provide a hollow container made of the copolymer polyester resin.

As a result of intensive studies aimed at eliminating the above-mentioned drawbacks, the present inventors have found that a copolymer polyester resin having a specific composition can achieve the above-mentioned problems, and have reached the present invention. That is, the present invention provides a copolyester having terephthalic acid or an ester derivative thereof as a main dicarboxylic acid and ethylene glycol as a main diol component, and (1) isophthalic acid or an ester derivative thereof as 2 to 16 as a dicarboxylic acid component. Mol%, and (2) as a trivalent acid component , trimellitic acid is included in an amount of 0.001 to 2 mol% based on the total amount of the acid component , and (3) an intrinsic viscosity of 0.9 to 1.5 dl / g, (4) The melt tension at 280 ° C., the extrusion speed of 15 mm / min, and the take-up speed of 15 m / min is in the range of 5 to 50 mN, and is a trimerit before the esterification reaction or transesterification reaction between the dicarboxylic acid and the diol component. The present invention relates to a copolyester resin produced by adding an acid.

The present invention also provides a dicarboxylic acid component containing terephthalic acid or an ester derivative thereof as a main component, a diol component containing ethylene glycol as a main component, and (1) 2 to 16 isophthalic acid or an ester derivative thereof as a dicarboxylic acid. Mol% and (2) 0.001 to 2 mol% of trimellitic acid as a trivalent acid component with respect to the total amount of the acid component are simultaneously charged into the reaction apparatus, subjected to esterification or transesterification, and further melted The present invention relates to a method for producing a copolyester resin, characterized by carrying out a polymerization reaction and then a solid phase polymerization reaction.
Moreover, this invention relates to the hollow container which consists of the said copolyester resin.

  According to the copolymerized polyester resin of the present invention, it is possible to produce an extrusion blow-molded product (hollow container) having good transparency and excellent color tone with good moldability.

Hereinafter, the present invention will be described in detail.
In the copolyester resin of the present invention, the raw materials used in known PET resins may be used for the main components terephthalic acid and ethylene glycol. The proportion of (1) isophthalic acid or its ester derivative used for copolymerization is in the range of 2 to 16 mol%, preferably 3 to 10 mol% as the dicarboxylic acid component. (1) When the proportion of isophthalic acid is less than the above range, whitening occurs in the bottle due to the formation of spherulites during extrusion blow molding, and poor molding tends to occur. On the other hand, when the above range is exceeded, sufficient mechanical strength cannot be obtained when a molded article such as a container is formed. In addition, since the melting point of the prepolymer obtained by melt polymerization is lowered, sticking easily occurs between the prepolymer chips during the subsequent precrystallization and solid phase polymerization, and the solid phase polymerization temperature is lowered. Therefore, there are problems that the polymerization rate is remarkably reduced, the productivity is deteriorated, and the solid phase polymerization becomes impossible because of the amorphous state. From the point that whitening of the bottle and poor shaping are prevented, sufficient mechanical strength is obtained, there is no sticking between the prepolymer chips during precrystallization and solid phase polymerization, and the productivity is good. (1) The proportion of isophthalic acid is in the range of 2 to 16 mol%, preferably 3 to 10 mol% as the dicarboxylic acid component.

  The copolymer polyester resin of the present invention further comprises (2) 0.001 to 2 mol% of trimellitic acid as a trivalent acid component with respect to the total amount of the acid component. (2) When the content of trimellitic acid is less than 0.001 mol% with respect to the total amount of the acid component, the drawdown of the parison becomes severe during extrusion blow molding, resulting in poor molding. On the other hand, when it exceeds 2 mol% with respect to the total amount of the acid component, a crosslinking reaction proceeds during the polymerization and a gelled product is generated. Therefore, an undissolved product is formed when the bottle is molded, and the appearance of the bottle is significantly impaired. In addition, since the solid phase polymerization rate is increased, it is difficult to adjust the polymerization degree.

  In the copolyester of the present invention, (3) the intrinsic viscosity at 20 ° C. in a 60/40 (mass ratio) phenol / tetrachloroethane mixed solvent is within the range of 0.8 dl / g to 1.5 dl / g. is there. When the intrinsic viscosity is less than 0.8 dl / g, the drawdown of the parison becomes severe during extrusion blow molding, resulting in poor molding, and mechanical performance such as impact resistance becomes insufficient. If the intrinsic viscosity is greater than 1.5 dl / g, the time required for solid-phase polymerization becomes longer, the color tone is deteriorated, and an unmelted product or the like is generated, thereby impairing the appearance of the molded product. Further, since the screw torque becomes high when the resin is melt-extruded, a problem arises in molding or productivity is lowered, which is not preferable.

  In the copolyester of the present invention, (4) the melt tension at 280 ° C., the extrusion speed of 15 mm / min, and the take-up speed of 15 m / min is in the range of 5 to 50 mN. When the melt tension is less than 5 mN, the drawdown of the parison melted at the time of extrusion blow molding becomes severe, which is not preferable. On the other hand, if it exceeds 50 mN, the elasticity of the melted parison becomes so high that blow is not possible, which is not preferable.

  In the production of the copolyester resin of the present invention, (2) trimellitic acid may be introduced into the reactor before the esterification reaction or transesterification reaction between the dicarboxylic acid component and the diol component. preferable. By charging the pre-reaction stage, that is, simultaneously with the dicarboxylic acid component and the diol component, the reaction can proceed while being uniformly dispersed in the resin. On the other hand, charging in the middle of the esterification reaction or transesterification reaction is not preferable because water and alcohol are volatilized by the reaction. In addition, it is not preferable that the esterification or transesterification reaction is performed before the polymerization step, because the uniform dispersion of trimellitic acid is insufficient and a gel is easily formed, and the appearance may be poor when molded.

As a method for producing the copolymer polyester of the present invention, melt polymerization and subsequent solid phase polymerization can be applied by a known polyester production method. The production method will be described in detail below.
Melt polymerization is a direct polymerization method in which a dicarboxylic acid and a diol are esterified and then subjected to a melt polycondensation reaction, or a transesterification method in which an ester derivative compound of a dicarboxylic acid and a diol are subjected to an ester exchange reaction and then a melt polycondensation reaction. Do it by either. In solid phase polymerization, the polymer obtained by melt polymerization is heated to a temperature below the melting point or softening point under reduced pressure or under an inert gas flow to obtain a polyester having a desired degree of polymerization.

As an example of the melt polymerization method, an example of a method of producing by using terephthalic acid, ethylene glycol, isophthalic acid, and trimellitic acid as raw material monomers is shown below. A mixture of dicarboxylic acid composed of terephthalic acid and isophthalic acid, ethylene glycol and trimellitic acid, the total amount of diol components is an excess molar amount relative to the total amount of the dicarboxylic acid, for example, 1.1 to 1.5 times mol. At such a rate, esterification is carried out while distilling water produced at a temperature of about 230 to 280 ° C. under normal pressure or under a pressure of about 3 kg / cm ² or less in absolute pressure, followed by polycondensation if necessary. After adding an additive such as a catalyst and an anti-coloring agent, it is subjected to melt polycondensation at about 200 to 280 ° C. under a reduced pressure of 5 mmHg or less until the resulting polyester has a desired intrinsic viscosity to obtain a polymer.

  Known polycondensation catalysts may be used in a wide range, but typical examples include antimony compounds such as antimony oxide; germanium compounds such as germanium oxide; tetramethoxy titanium, tetraethoxy titanium, tetra n-propoxy titanium, tetra Examples thereof include titanium compounds such as isopropoxy titanium and tetrabutoxy titanium; tin compounds such as di-n-butyltin dilaurate, di-n-butyltin oxide and dibutyltin diacetate, and these catalysts can be used in combination. In addition, it is preferable to use the said polycondensation catalyst in the quantity which will be in the range of 0.001-0.8 mass% with respect to the copolyester resin to each produce | generate.

  In the present invention, a known stabilizer may be used. Phosphorous acid, phosphoric acid, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, triethyl phosphate, tridecyl phosphate, tridecyl phosphate Phosphorus compounds such as phenyl phosphate are exemplified, and it is generally used in such an amount that it is in the range of 0.001 to 0.5% by mass with respect to the copolymer polyester to be produced.

  The copolymerized polyester polymer obtained as described above is usually melt-extruded into a strand shape, solidified into an arbitrary shape, cut and formed into a granular pellet. Next, the pellet is preliminarily crystallized by heating to a temperature lower than the temperature at which solid phase polymerization is performed in advance so that the pellets do not stick together. Such a precrystallization step can be performed by heating the copolymerized polyester chip to a temperature of usually 100 to 180 ° C., preferably 110 to 160 ° C. for 1 minute to 10 hours, or the chip can be heated with hot water or water vapor. Or it can also carry out by heating to the temperature of 90-140 degreeC for 1 minute or more in water vapor containing inert gas atmosphere. By being crystallized, sticking between pellets can be prevented.

The pellet preliminarily crystallized as described above is sent to a solid phase polymerization step. The polymerization temperature is 190 to 235 ° C., preferably 195 to 230 ° C., and at an arbitrary pressure of 1 kg / cm ² G to 0.01 torr, or under a flow of an inert gas such as nitrogen, argon, carbon dioxide or the like Performed in an atmosphere without. The polymerization time reaches the desired physical properties in a shorter time as the temperature is higher, but is usually 1 to 80 hours, preferably 5 to 50 hours.

  As described above, the copolymerized polyester resin of the present invention starts with terephthalic acid or an ester derivative thereof such as dimethyl ester or diethyl ester, (1) isophthalic acid or an ester derivative thereof, ethylene glycol, and (2) trimellitic acid. Although it can manufacture using it as a raw material, you may use together another monomer according to the objective. Examples of acid component monomers that can be used in combination include phthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and aromatic dicarboxylic acids such as sodium-sulfoisophthalic acid; malonic acid, succinic acid Aliphatic dicarboxylic acids such as acids, adipic acid, azelaic acid and sebacic acid; alicyclic dicarboxylic acids such as decalidicarboxylic acid and cyclohexanedicarboxylic acid; and glycolic acid, hydroxyacrylic acid, hydroxypropionic acid, asacic acid, quinova One or more selected from hydroxycarboxylic acids such as acid, hydroxybenzoic acid, mandelic acid, and matrolactic acid; aliphatic lactones such as ε-caprolactone, and the amount used is the total acid component Preferably 5 mol% or less against. Alcohol component monomers that can be used in combination include aliphatic diols such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, diethylene glycol, and polyethylene glycol; hydroquinone, catechol, naphthalenediol, resorcin, bisphenol A, bisphenol A One or more types selected from aromatic diols such as ethylene oxide adducts, bisphenol S, and ethylene oxide adducts of bisphenol S, and the amount used is preferably 5 mol% or less based on the total alcohol components. A small amount of a trivalent or higher carboxylic acid such as pyromellitic acid or tricarballylic acid can also be used.

  The copolymerized polyester of the present invention can be obtained by appropriately selecting the conditions for the melt polymerization and solid phase polymerization treatment. The amount of by-products such as cyclic oligomers and acetaldehyde remaining in the polymer is considerably smaller than that of the melt-polymerized product due to solid phase polymerization. The copolyester of the present invention thus obtained is preferably used in producing a bottle (hollow container) by direct blow molding. The molding temperature can be set to 5 to 20 ° C. lower than that of PET for general bottles, and the thermal deterioration can be suppressed to a low level within the range of 250 to 280 ° C. for each part of the cylinder and the nozzle. Therefore, the amounts of oligomers and acetaldehyde that are by-produced during molding are also low and can be easily suppressed.

  The hollow container of the present invention may be a composite (blend or multilayer) with a gas barrier resin such as polyethylene terephthalate or EVOH as well as a single-layer bottle made of the above-mentioned copolymerized polyester. In addition, the above copolyester, if necessary, within a range that does not impair the effects of the present invention, a small amount of other thermoplastic resins are used in combination, or substances that are generally added to thermoplastic resins, That is, stabilizers such as ultraviolet absorbers, antistatic agents, flame retardants, flame retardants, colorants such as dyes and pigments, lubricants, plasticizers, inorganic fillers, and the like can be blended.

  The hollow container obtained by molding the copolymerized polyester of the present invention is a hollow container with excellent formability and transparency, which overcomes the drawbacks of conventional polyethylene terephthalate or polyethylene terephthalate copolymer. It is useful as various containers.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In addition, the measurement conditions of the characteristic value in an Example and a comparative example are as follows.
<Resin physical properties after solid-phase polymerization>
(1) Intrinsic viscosity;
0.5 g of a copolymer polyester resin sample of each example and comparative example was precisely weighed and dissolved in 50 ml of a mixed solvent of phenol / tetrachloroethane = 60/40 (mass ratio), and at 20 ° C. using an Ostwald viscometer. It was measured. In addition, the measurement was performed 3 times and it calculated | required from the average value.
(2) Melt viscosity (melt tension)
About the copolymer polyester resin of each Example and the comparative example, the melt tension in 280 degreeC, the extrusion speed of 15 mm / min, and the take-up speed of 15 m / min was measured using the Toyo Seiki Capillograph 1B.

<Moldability and molded product characteristics>
The copolymer polyester resin of each Example and Comparative Example was supplied to an extrusion blow molding apparatus (JEB3 manufactured by Nippon Steel Works) and extruded from an annular orifice at an extrusion temperature of 260 ° C. to form a cylindrical parison. By sandwiching with a blow mold in the softened state, cutting and bottom formation were performed, and this was blow molded to form a bottle having a capacity of 500 ml and an average wall thickness of 0.2 mm. The drawdown property of the parison at that time, transparency after blow molding, the presence or absence of an appearance gel-like material, and thickness spots were evaluated. These evaluation results were evaluated according to the evaluation criteria shown below.

(1) Drawdown property;
○ ・ ・ ・ Cylindrical shape of extruded parison with substantially uniform diameter Δ ・ ・ ・ Drawdown of extruded parison is severe, impossibility of insertion into blow mold, or obstruction in hollow part of parison Occasional occurrence x ... The extruded parison draws down drastically and cannot be inserted into the blow mold, or the parison is frequently clogged (2) Transparency of the molded product;
○ ・ ・ ・ Transparency of blow molded product is good Δ ・ ・ ・ After blow molding, there is a partially white cloudy part × ・ ・ ・ After blow molding, a dark cloudy part is observed

(3) Appearance, gel-like presence / absence ○ ・ ・ ・ Transparency of the appearance of blow-molded product is good Δ ・ ・ ・ Partial gel-like material after blow molding × ·············· Blow molding 4) Thickness unevenness ○ ・ ・ ・ Molded in a bottle without thickness unevenness Δ ・ ・ ・ Thin portions with a thickness of 0.1 mm or less occur, or broken portions sometimes occur ×× Thin portions with a thickness of 0.1 mm or less Or damaged parts occur frequently

Example 1 A slurry consisting of 97.9 mol% terephthalic acid, 2 mol% isophthalic acid, 0.1 mol % trimellitic acid, and 100 mol% ethylene glycol was formed, and this slurry was pressurized (absolute pressure 2. 5 kg / cm ² ) at a temperature of 250 ° C. until the esterification rate reached 95%, to produce a low polymer. A polymer of copolymerized polyester having an intrinsic viscosity of 0.61 dl / g by adding 150 ppm germanium dioxide and 100 ppm phosphoric acid compound to the obtained polymer and polycondensing it at a temperature of 280 ° C. under a reduced pressure of 1 torr absolute. Got. The obtained prepolymer was extruded into a strand form from a nozzle and cut to produce a cylindrical chip (diameter 2.5 mm, length 3.5 mm). The prepolymer chip thus obtained was pre-crystallized and then pre-dried at 150 ° C. for 5 hours, and then subjected to solid phase polymerization at a temperature of about 20 ° C. lower than the melting point (220 ° C.) under a reduced pressure of 0.1 mmHg. A polyester resin was obtained. The intrinsic viscosity of this polyester was 1.1 dl / g.

  Examples 2 to 7 and Comparative Examples 1 to 9: Reaction was carried out in the same manner as in Example 1 except that the amounts of terephthalic acid, ethylene glycol, isophthalic acid and trimellitic acid were changed to the values shown in Table 1. Copolyester resins having various composition ratios were obtained. Characteristic evaluation was performed about each obtained polyester resin. The evaluation results are also shown in Table 1. However, in Comparative Example 4, since the obtained polyester resin was amorphous, solid phase polymerization could not be performed, and molding evaluation could not be performed.

  In each of Examples 1 to 7, good moldability and molded product appearance could be obtained. On the other hand, when no trimellitic acid was blended as in Comparative Examples 1 and 2, moldability defects and thickness spots occurred due to drawdown. Moreover, when isophthalic acid was not mix | blended like the comparative example 3, it was inferior to the transparency of a molded article. When there was much isophthalic acid like the comparative example 4, since crystallization was difficult, solid phase polymerization itself was not able to be performed. In Comparative Example 5, since there was much trimellitic acid, gelation was severe and both moldability and appearance were poor. In Comparative Example 6, since the viscosity of the resin itself was low, poor moldability and thickness unevenness due to drawdown occurred. In Comparative Example 7, the resin had a high viscosity, and it was difficult to mold unless the melting temperature was increased. In Comparative Examples 8 to 9, trimellitic acid was blended after esterification, but the appearance of the molded product was poor.

Claims (3)

A copolymer polyester resin having terephthalic acid or an ester derivative thereof as a main dicarboxylic acid and ethylene glycol as a main diol component,
(1) 2 to 16 mol% of isophthalic acid or an ester derivative thereof as a dicarboxylic acid component;
(2) As a trivalent acid component , trimellitic acid is contained in an amount of 0.001 to 2 mol% based on the total amount of the acid component ,
(3) Intrinsic viscosity is 0.9 to 1.5 dl / g,
(4) Melt tension at 280 ° C., extrusion speed 15 mm / min, take-off speed 15 m / min is in the range of 5 to 50 mN,
A copolyester resin produced by adding trimellitic acid before esterification reaction or transesterification reaction between the dicarboxylic acid and the diol component. A dicarboxylic acid component mainly composed of terephthalic acid or an ester derivative thereof, a diol component mainly composed of ethylene glycol, and
(1) 2 to 16 mol% of isophthalic acid or an ester derivative thereof as a dicarboxylic acid,
(2) As a trivalent acid component , trimellitic acid is added in an amount of 0.001 to 2 mol% with respect to the total amount of the acid component at the same time for esterification reaction or transesterification reaction, followed by melt polymerization reaction. Then, a method for producing a copolyester resin, wherein a solid phase polymerization reaction is performed thereafter.   A hollow container comprising the copolymerized polyester resin according to claim 1.