JP2000198837A - Polyester and its molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester having good color tone and suitable for molding causing little contamination of mold with cyclic trimers and provide a molded article made thereof. SOLUTION: The polyester is composed mainly of terephthalic acid and ethylene glycol and has an intrinsic viscosity of >=0.60. The polyester contains 1×10-4 to 7×10-4 mol of phosphorus element based on 1 mol of the total acid component of the polyester and 0.5×10-4 to 3×10-4 mol of germanium element based on 1 mol of the total acid component of the polyester. The molar ratio of the phosphorus element to the germanium element is >=1.6 and the content of cyclic trimers is <=0.4 wt.% based on the total polyester.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester which is excellent in color tone and transparency, has little mold contamination by a cyclic trimer, and is suitable for molded articles, and a molded article comprising the same.

[0002]

2. Description of the Related Art Polyethylene terephthalate (hereinafter P)
Abbreviated as ET. ) Are excellent in mechanical strength, chemical stability, transparency, etc., and are widely used for various sheets, films, containers, etc. because of their light weight and low cost. The use of containers for fruit juice drinks, liquid seasonings, edible oils, alcohol, wine, etc., is growing remarkably.

In general, a hollow container is formed by supplying PET to a molding machine such as an injection molding machine to form a preform, heating the preform, inserting the preform into a mold having a predetermined shape, and stretching and blowing. I do. However, in polyesters for molded articles (hereinafter abbreviated as polyester) used as raw materials for molded articles, oligomers typified by cyclic trimers of terephthalic acid and ethylene glycol (hereinafter abbreviated as CT). And these adhere to the surface of the mold, gas exhaust ports, exhaust pipes, and the like, so that mold contamination easily occurred. Since such mold contamination causes surface roughness and whitening of the obtained hollow container, it is necessary to frequently remove mold contamination, and there is a disadvantage that productivity is significantly reduced.

[0004] In addition to the above-described hollow container forming step, polyesters having a low CT content are desired because they cause whitening and dropout of the film.

As a method of reducing the CT content in polyester, a method of simply solid-phase polymerization (for example, see JP-A-53-1010).
No. 1092) and a method of extending the solid-state polymerization time by controlling the flow rate and pressure of nitrogen during the solid-state polymerization and suppressing an increase in the intrinsic viscosity to perform the de-CT process (for example, 55-8
No. 9330, Japanese Unexamined Patent Publication No. 55-89331) and the like have been proposed. However, in these methods, it is necessary to carry out solid phase polymerization for an extremely long time in order to sufficiently reduce the CT content, so that the productivity is poor and the color tone of the polyester is deteriorated.

Japanese Patent Application Laid-Open No. 9-221540 proposes a method of suppressing the CT content in polyester and the CT by-product during bottle molding by adding a specific amount of phosphorus element and germanium element to polyester. Have been. But,
By-product of CT during bottle molding is small, so it is not an important problem, and it is important to reduce CT content in polyester as much as possible.However, when the ratio of phosphorus element and germanium element shown here is 1.5 or less, Since the effect of reducing CT is not sufficient, there is a problem that the CT content in the polyester does not decrease.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides a polyester which is excellent in color tone and is suitable for molding with less mold contamination by CT, and a molded article comprising the same. It is a technical issue.

[0008]

Means for Solving the Problems The present inventors have set forth the above section.
As a result of intensive studies to solve the problem,
Was. That is, the present invention has the following configuration.
You. (1) Mainly terephthalic acid and ethylene glycol
In polyester, intrinsic viscosity is 0.60 or more, phosphorus element
1 × 10 ^-FourMole
~ 7 × 10^-FourMol, germanium element in all of the polyester
0.5 × 10 per mole of acid component^-FourMol ~ 3 x 10^-FourMorso
Each of which contains the phosphorus element relative to the germanium element.
Ratio is 1.6 or more, and the content of CT is
Less than 0.4% by weight
Le. (2) Injection molding or extrusion molding of the polyester described in (1) above
Molded product formed by shape.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The polyester of the present invention contains terephthalic acid (hereinafter abbreviated as TPA) as a dicarboxylic acid component and ethylene glycol (hereinafter abbreviated as EG) as a diol component.

The polyester may contain other copolymer components as long as its properties are not lost. Specific examples of the copolymer component include adipic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, diethylene glycol, 1,4-cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A or bisphenol S, and the like. No.

In the polyester of the present invention, the intrinsic viscosity must be 0.60 or more. If the intrinsic viscosity is less than 0.60, a molded product cannot have sufficient strength after processing.

It is important that the polyester of the present invention contains specific amounts of a phosphorus element and a germanium element. That is, the phosphorus element is converted to the total acid component 1 of the polyester.
1 × 10 ^-4 mol to 7 × 10 ^-4 mol per mol, 0.5 × germanium element per mol of all acid components of polyester
It is necessary to contain 10 ^-4 mol to 3 × 10 ^-4 mol, respectively. If the content of phosphorus element is less than 1 × 10 ^-4 mol, C
It is not preferable because the effect of reducing T is low. On the other hand, when the amount exceeds 7 × 10 ⁻⁴ mol, diethylene glycol is easily produced as a by-product, and the heat resistance of the polyester is undesirably reduced. Examples of the phosphorus element include phosphoric acid, a phosphoric ester, a phosphate, phosphorous acid, a phosphite, and the like, and phosphoric acid is preferred in terms of cost.

Next, the content of the germanium element is 0.5 ×
If the amount is less than 10 ^-4 mol, the polymerization rate is slow and the polymerization time is prolonged. As a result, the color tone is deteriorated or the productivity is deteriorated, which is not preferable. On the other hand, if it exceeds 3 × 10 ⁻⁴ mol, the polymerization rate is not changed and the cost is increased, which is not preferable. Examples of the germanium element include germanium dioxide, germanium chloride, germanium tetraethoxide, and germanium tetra-n-butoxide. Germanium dioxide is preferable in that a polyester having excellent color tone and transparency can be obtained.

Further, it is important for the polyester of the present invention that the molar ratio of the phosphorus element to the germanium element is at least a certain amount, and the molar ratio must be at least 1.6. The germanium element acts as a catalyst for the ring-opening reaction of CT during solid-state polymerization, and the phosphorus element acts as a co-catalyst. When the molar ratio of the phosphorus element to the germanium element is less than 1.6, the effect of the phosphorus element as a cocatalyst is not sufficient, and the CT reduction during the solid phase polymerization becomes insufficient.

The polyester of the present invention must have a CT content of 0.4% by weight or less based on the total polyester. When the content of CT exceeds 0.4% by weight,
Contamination of the mold and the like during molding becomes remarkable, which is not preferable.

The polyester of the present invention can be produced by a conventional method, for example, as follows. TPA and EG are charged into an esterification reactor at a predetermined ratio, and an esterification reaction is performed under pressure at a temperature of 160 to 280 ° C. Then, the obtained polyester oligomer is transferred to a polymerization reactor, and germanium element is used as a polymerization catalyst. A phosphorus element is added as an additive, and the melt polymerization reaction is carried out at a temperature of 250 to 300 ° C., preferably 260 to 290 ° C., usually under a reduced pressure of 1 hPa. Note that additives such as an antioxidant and a pigment can be added as needed during the esterification reaction or the polymerization reaction.

The polyester obtained by the melt polymerization reaction contains CT and aldehydes at all. Also, when the degree of polymerization is increased by using solid-phase polymerization in combination with melt polymerization,
A polyester having good color tone and transparency can be obtained. Therefore,
After the polyester obtained by melt polymerization is formed into pellets, it is preferable to carry out solid phase polymerization to obtain a polyester having a high degree of polymerization required for molding and to reduce the CT content.

In the solid phase polymerization, the polyester pellets are preliminarily crystallized by heating them in a dry state at a temperature of 100 to 180 ° C. for 0.5 to 8 hours, and then at 190 to 235 ° C. under an inert gas flow. It is carried out by heating under reduced pressure or under reduced pressure for 1 to 50 hours, preferably 5 to 30 hours.

The polyester of the present invention obtained by the above method or the like can be formed into a molded article such as a hollow container by the following method. For example, a hot parison method in which a preform is formed by injection molding or extrusion molding and the preform is reheated and biaxially stretched, or a cold preform in which the plug and bottom of the preform are preheated and then biaxially stretched The parison method or the like can be applied.

At this time, the molding temperature at the time of injection molding or extrusion molding, specifically, the temperature of each part of the cylinder and the nozzle of the molding machine is usually in the range of 270 to 300 ° C. Also,
The stretching temperature is usually 70 to 120 ° C, preferably 80 to 110 ° C.
The stretching ratio is 1.5 to 3.5 times in the longitudinal direction and 2 to
A range of 5 times is appropriate.

The hollow container thus obtained can be used as it is. In particular, in the case of a content liquid that requires hot filling such as a fruit juice beverage, the hollow container generally contains the same blow mold used for molding. , Or heat set in a separately provided mold,
Used with improved heat resistance. This method of heat setting
Generally, under tension due to compressed air, mechanical elongation, etc., usually at 100 to 200 ° C, preferably at 120 to 180 ° C,
It is performed for 2 seconds to 2 hours, preferably for 10 seconds to 30 minutes.

[0022]

Next, the present invention will be described in detail with reference to examples. In addition, the characteristic value of polyester was measured as follows. (a) Intrinsic viscosity [η] Measured at a temperature of 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent. (b) Content of germanium element and phosphorus element The content was measured using a fluorescent X-ray analyzer 3270 manufactured by Rigaku Corporation. (c) CT content in polyester Hexafluoroisopropanol / chloroform (1: 1, volume ratio) in polyester pellet or hollow container
The polymer component was precipitated by adding acetonitrile, and the filtrate filtered with a membrane filter was analyzed by high performance liquid chromatography (Waters 600E). (d) Color tone of polyester It was measured using a color difference meter ND- # 80 manufactured by Nippon Denshoku Industries Co., Ltd. The color tone was determined using a Hunter Lab colorimeter.
A b value of 1.0 or less was regarded as a pass. (e) Plate haze Extrude the dried polyester at 285 ° C, mold temperature
Under a condition of 20 ° C. and a cooling time of 30 seconds, injection molding was performed on a plate having a thickness of 5 mm × length 10 cm × width 6 cm, and the transparency was evaluated using a turbidity meter MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (air: haze 0).
%). The smaller this value is, the better the transparency is, and if it is less than 10%, it is acceptable. (f) Presence or absence of mold contamination After continuous molding of 20,000 hollow containers from polyester, the mold was visually observed to check for oligomer precipitation.

EXAMPLE 1 Germanium dioxide was added to 60 kg of a PET oligomer obtained by a conventional method so that the content of germanium element was 1.1 × 10 ⁻⁴ mol per 1 mol of the total acid component of the polyester. Phosphoric acid was added so that the phosphorus element content was 2.9 × 10 ^-4 mol per 1 mol of the total acid component, and the pressure was reduced in the polymerization reactor.
Polycondensation was performed at ℃ to obtain a prepolymer having an intrinsic viscosity of 0.55. The prepolymer was pre-dried, subsequently crystallized and dried, and then subjected to solid-state polymerization at 230 ° C. to obtain a polyester having an intrinsic viscosity of 0.78. The CT content of the obtained polyester was 0.30% by weight, and the b value was 0.5.

After crystallization and drying of the polyester, the temperature of the cylinder and nozzle of the molding machine was reduced to 280.
A plate was obtained by performing injection molding at ℃. Also, a preform was obtained in the same manner, and the preform was stretched at a stretching temperature of 100 ° C., a stretching ratio of 2 times in the longitudinal direction, and 3 times in the circumferential direction, to obtain a hollow container. Although 20,000 hollow containers were continuously formed, no contamination of the mold was observed.

Examples 2-3 A polyester was produced in the same manner as in Example 1 except that the addition amounts of phosphoric acid and germanium dioxide and the intrinsic viscosity were changed as shown in Table 1, and then a plate was prepared using this polyester. , A hollow container was prepared, and the characteristics were evaluated. Table 1 also shows the evaluation results.

Comparative Example 1 The procedure of Example 1 was repeated, except that the solid-phase polymerization was not performed, and only the esterification reaction and the melt polymerization were performed.

Comparative Examples 2 to 4 A polyester was produced in the same manner as in Example 1 except that the addition amounts of phosphoric acid and germanium dioxide and the intrinsic viscosity were changed as shown in Table 1, and then a plate and a hollow container were produced. Then, the characteristics were evaluated. Table 1 also shows the evaluation results.

[0028]

[Table 1] As is clear from Table 1, the polyesters obtained in Examples 1 to 3 have an intrinsic viscosity of 0.60 or more and a CT content of 0.40.
% Or less, and the molded article had a plate haze of 2.2% or less, good transparency, and no mold contamination was observed.

On the other hand, Comparative Example 1 has a low intrinsic viscosity,
The reduction of T content is not enough, there is mold contamination,
The transparency of the molded article was also poor. In Comparative Example 2, since the content of the phosphorus element was small, the reduction of the CT content was not sufficient, and mold contamination was observed. Next, in Comparative Example 3, since the content of the germanium element was small and the polymerization time was long,
The color was inferior. Furthermore, in Comparative Example 4, the CT content was not sufficiently reduced because the molar ratio of the phosphorus element to the germanium element was small, and mold contamination was observed.

[0030]

According to the present invention, a polyester having a good color tone and a low CT content is provided. If a hollow container is molded using this polyester, contamination of a molding die by CT is prevented. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C08L 67:02 F term (reference) 4F071 AA46 AA81 AC10 AF10 AF29 AF55 AH05 BA01 BB05 BB06 BB08 BC04 4J002 CF061 DD077 DE097 DH026 EC077 EH148 EW046 EW066 GG01 4J029 AA03 AB01 AB07 AC01 AD01 AD10 AE01 BA03 CB06A JA061 JA091 JA251 JA261 JB131 JC571 JC581 JF361 KB05

Claims (2)

[Claims] 1. A polyester containing terephthalic acid and ethylene glycol as main components, having an intrinsic viscosity of 0.60 or more, and a phosphorus element in an amount of 1 × 10 ^-4 mol to 7 × 10 ^-4 mol per 1 mol of all acid components of the polyester. And germanium element in an amount of 0.5 × 10 ^-4 mol to 3 mol per mol of the total acid component of the polyester.
A polyester characterized by containing each of × 10 ^-4 mol and having a molar ratio of phosphorus element to germanium element of 1.6 or more and a cyclic trimer content of 0.4% by weight or less based on all polyesters. 2. A molded article obtained by molding the polyester according to claim 1 by injection molding or extrusion molding.