JP2000237707A - Method for cleaning polyester resin vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning a polyester resin vessel with the surface deteriorated by the irradiation with UV without lowering the transparency of the vessel. SOLUTION: When a repeatedly used polyester resin vessel is cleaned, the surface of the vessel is cleaned by a hot aq.soln. of surfactant having 6<PH<8 at ordinary temps. and then cleaned with water or hot water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a polyester resin container. More particularly, the present invention relates to a method for cleaning a polyester resin container which is used repeatedly without reducing the transparency.

[0002]

2. Description of the Related Art When a beverage or the like is filled and shipped to the market, the used polyester resin container is collected, and the container shape is used again for recycling (repeated use).
The collected container has been washed with an aqueous alkali solution such as sodium hydroxide. For example, a container made of polyethylene terephthalate resin is collected from the market, washed with an alkali, filled again with a beverage or the like, and shipped to the market. However, this collection and reuse may be about 10 times. The number of reuses depends on the mechanical properties of the container, the presence or absence of
It is determined by polymer deterioration or the like. Factors of this deterioration include deterioration due to exposure to sunlight, deterioration due to alkali cleaning, and the like. However, in the case of polyethylene terephthalate resin containers, the ultraviolet ray deterioration and alkali deterioration do not become a problem and are not evident after about 10 times of collection and reuse.

In recent years, attention has been paid to polyethylene-2,6-naphthalenedicarboxylate resin (PEN) as a polymer having better mechanical and thermal properties than polyethylene terephthalate resin (PET). Are being considered. This PEN container is expected to increase the number of times of collection and reuse.

However, in the development of PEN containers,
The collected PEN container is washed with alkali, for example, 50 to 9
It was clarified that the transparency was reduced as the alkali washing was performed with a 1 to 6% aqueous sodium hydroxide solution heated to 5 ° C. Further, it has been revealed that the lowering of the transparency becomes more remarkable as the number of times of recycling the PEN containers recovered from the market is washed with alkali and reused.

[0005]

As a result of intensive studies to solve this problem, the present inventor has found that the surface of a PEN container is deteriorated by ultraviolet rays during distribution on the market and during storage after recovery. It has been found that such a portion is easily peeled off by washing with an alkaline aqueous solution, and that the deterioration and peeling become remarkable due to repetition of recycling, thereby lowering the transparency.
On the other hand, the fact that such a problem has not been apparent in a PET container is that PET has excellent weather resistance and alkali resistance.
It has been found that the recovery and reuse of about 0 times is due to small deterioration of ultraviolet rays and alkali. However, this degradation will become more evident as the number of recycles increases. Then, the present inventors have found a cleaning method that does not reduce the transparency of the container, and a container that has good transparency and has a small remaining amount of organic substances adsorbed thereon, and has completed the present invention.

An object of the present invention is to provide a cleaning method which does not reduce the transparency of a container made of a polyester resin, and a container which has good transparency even when used repeatedly.

[0007]

According to the present invention, when washing a polyester resin container which is used repeatedly, the pH of the container at 25 ° C. is determined by the following formula (1). This is achieved by a method for washing a polyester resin container, characterized by washing with a warmed aqueous solution of a surfactant and further washing with water or hot water.

[0008]

2 <pH <8 (1)

Hereinafter, the present invention will be described. As the polyester resin in the present invention, a polyester resin whose main repeating unit is composed of ethylene naphthalenedicarboxylate is targeted, and a polyester resin whose main repeating unit is composed of ethylene-2,6-naphthalenedicarboxylate is particularly preferable. Here, “main” means more than 80 mol% of all repeating units, preferably 85 mol%.
Say to exceed. Therefore, other components of 20 mol% or less may be copolymerized, or may be contained as a mixture. For example, in the case of polyethylene-2,6-naphthalenedicarboxylate copolymer, 2,6-
Part of naphthalenedicarboxylic acid component (20 mol% or less)
With 2,7-, 1,5-, 1,7-other isomers of naphthalenedicarboxylic acid, or terephthalic acid, isophthalic acid,
Other aromatic dicarboxylic acids such as diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, etc.
Alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid and azelaic acid, p-β
-It may be replaced by other bifunctional carboxylic acids such as oxyacids such as -hydroxyethoxybenzoic acid and ε-oxycaproic acid. Furthermore, part of the ethylene glycol component,
For example, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentyl glycol, diethylene glycol, 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2-bis (4′-β- A copolymer obtained by substituting at least one kind of another polyfunctional compound such as (hydroxyphenyl) propane and bis (4′-β-hydroxyethoxyphenyl) sulfonic acid and copolymerizing it in the range of 20 mol% or less may be used. . The same applies to other copolymers.

[0010] The polyester resin can be produced according to a known method. For example, polyethylene
2,6-naphthalenedicarboxylate resin (PEN)
First, 2,6-naphthalenedicarboxylic acid or its ester-forming derivative (preferably, dimethyl ester) and ethylene glycol are esterified or transesterified with heating under heating. In that case, it is preferable to use cobalt, manganese, calcium, magnesium, a titanium compound, etc. as a transesterification catalyst. Subsequently, a polycondensation reaction is performed under heating and vacuum in the presence of germanium, antimony, a titanium catalyst, and a phosphorus compound to obtain a polymer (PEN). As the phosphorus compound, an inorganic phosphoric acid such as orthophosphoric acid, hypophosphorous acid, and phosphorous acid, and an organic phosphoric acid such as trimethyl phosphate are preferably used. Then, if desired, the polymer may be formed into chips or pellets and subjected to solid-phase polymerization according to a conventional method. In order to obtain a polymer having a high degree of polymerization, it is preferable to carry out solid phase polymerization. This solid-phase polymerization also has the effect of reducing the amount of acetaldehyde and oligomer in the polymer. The intrinsic viscosity of the polymer (a mixed solvent of 2 parts by weight of trichlorophenol and 3 parts by weight of phenol at 25 ° C.) is 0.5
5 or more, more preferably 0.60 or more. The upper limit depends on the characteristics and moldability of the container, but is preferably 0.90, more preferably 0.80.

The polyester resin container of the present invention can be manufactured by a known method using the polyester resin. For example, it can be molded and manufactured by a method such as orientation stretch blow, direct blow and the like. As the container, a beverage bottle is most preferable, but a bottle for other uses may be used.

The polyester resin container of the present invention is a container that is repeatedly recovered and used, and washing is usually performed on a container recovered from the market. It may be carried out on a container that is soiled during the manufacturing process.

The washing is carried out with a warmed aqueous solution of a surfactant, and the temperature of the aqueous solution is preferably in the range of 50 ° C. to 100 ° C., more preferably 65 ° C. to 95 ° C.
If the temperature is too low, cleaning and sterilizing effects cannot be expected, and if the temperature is too high, thermal deformation of the container is caused, which is not preferable. The washing time depends on the washing temperature and the concentration of the surfactant, but is preferably from 5 minutes to 60 minutes, more preferably from 8 minutes to 20 minutes. If the time is short, cleaning and sterilizing effects cannot be expected, and if it is too long, thermal deformation of the container may be caused, and the process time may be long, which is not preferable. The pH of the surfactant used at room temperature (25 ° C.) of the aqueous solution is represented by the following formula (1).

[0014]

## EQU3 ## It satisfies 6 <pH <8 (1) and further, from the viewpoint of the cleaning effect, the following formulas (2) to (4)

[0015]

Embedded image

However, in these formulas, M is Na, K or Ca, R is CH ₃ (CH ₂ ) _m CH ₂ —, m is a number of 9 to 28, X is H or —CH ₂ CH ₂ OH. is there.

It is preferred to be selected from the compounds represented by It is preferable to use at least one of these compounds.

Specific examples of these surfactants include R.O.
As higher alcohol sulfates such as SO ₃ M, for example, lauryl sulfate, myristyl sulfate, palmityl sulfate, cetyl sulfate,
Examples include sodium, potassium, calcium salts of stearyl sulfate, oleyl sulfate, behenyl sulfate, seryl sulfate and myrisyl sulfate.

Examples of the polyoxyethylene alkyl ether such as RO (CH ₂ CH ₂ O) _n H include, for example, polyoxyethylene lauryl ether, polyoxyethylene myristyl ether, polyoxyethylene palmityl ether, polyoxyethylene cetyl ether. , Polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, polyoxyethylene seryl ether, polyoxyethylene myricyl ether, and the like.

Also, Examples of the fatty acid alkanolamides include lauric acid, mystic acid, palmitic acid, cetiric acid, stearic acid, oleic acid, and behenic acid ethanolamide and diethanolamide.

As described above, the pH of the cleaning aqueous solution must satisfy the formula (1).
It is not preferable because the surface of the container is roughened by washing, and the transparency is reduced. The concentration of the surfactant in the aqueous solution is preferably in the range of 0.02 to 10% by weight, more preferably 0.05 to 5.0% by weight. If the concentration is too low, the cleaning effect cannot be expected, while if it is too high, foam is remarkably generated and the detergent remains, which is not preferable. Further, the cost becomes high economically, which is not preferable.

The polyester resin container of the present invention is usually subjected to ultraviolet irradiation (usually irradiation with sunlight) during the period from the previous washing to filling, shipping, collection, and subsequent washing. It is preferable that the amount of ultraviolet light received during this period is as small as possible. The effect of the present invention becomes more remarkable as the container is repeatedly used and the deterioration of ultraviolet rays is advanced. However, even if the container has been collected and used only once, the effect of the present invention is remarkable even when the amount of received ultraviolet light is large and the deterioration of ultraviolet light is advanced. The number of times of collection and use can be easily determined by the number of the marks, for example, if a mark is written on the bottom of the container before washing, filling, and shipping.

The polyester resin container of the present invention is used repeatedly. The haze of the container after repeated use of 15 times is preferably 15% or less, more preferably 10% or less. This haze is 15%
When it exceeds, transparency is lowered, which is not preferable.

The method of cleaning the container in the present invention is not particularly limited as long as the heated aqueous solution of the surfactant comes into contact with the container. Most preferably, it is performed by immersion. In some cases, for example, a heated aqueous solution can be injected into the container. However, in this case, since the generation of bubbles is remarkable, a measure for preventing or reducing this will be required.

After washing with the warming aqueous solution, washing with water or warm water is performed. The temperature of the hot water is preferably 95 ° C. or less. The washing with water or hot water may be performed to such an extent that the heated aqueous solution can be sufficiently washed away.

The cleaning effect of the present invention is as follows. A heated aqueous solution of a surfactant is brought into contact with a polyester resin container,
Further, after washing with water or hot water, the remaining amount of methanol adsorbed is 3,500 ppm or less, and the remaining amount of m-xylene adsorbed is 1
It is preferably at most 00 ppm. If the residual amount of methanol exceeds 3,500 ppm or the residual amount of m-xylene exceeds 100 ppm, it is not preferable in view of the residual odor of the container. Here, the residual amount of methanol and m-xylene is defined as the polyester resin container immersed in the methanol or m-xylene for 7 days, washed, air-dried, and headspace gas chromatograph (sample heating temperature 150 ° C). ° C).

[0027]

EXAMPLES The present invention will now be described more specifically with reference to examples, but the present invention is not limited to the examples. The characteristics in the examples were measured by the following methods.

(1) pH The pH of the washing solution was determined by Castany LAB manufactured by HORIBA.
It measured at 25 degreeC with pH meter (F-14).

(2) Polymer intrinsic viscosity Mixed solvent (2: 3 of trichlorophenol and phenol)
Was measured at 25 ° C.

(3) Haze One body (thickness: about 300 μm) of the bottle was set with a turbidimeter and measured.

(4) Ultraviolet irradiation Irradiated with ultraviolet rays (xenon tester; Shimadzu xenon tester XW-150) was applied to the sample from the body of the bottle. The illuminance of the ultraviolet rays (310 to 400 nm) was measured with a MINORUTA UV intensity meter UM-10 (light receiving unit UM-360).

(5) Amount of methanol and m-xylene adsorbed The bottle was filled with methanol or xylene and held for 7 days, then the filled methanol or xylene was taken out, air-dried, and immersed in a washing solution at 82 ° C. for 10 minutes. And washed. After the treatment, it was washed with water, and the amounts of methanol and m-xylene were measured by a head space gas chromatography (sample heating temperature: 150 ° C.).

[Examples 1 to 6, Comparative Examples 1 and 2] Preparation of polymer 2,6-naphthalenedicarboxylic acid dimethyl ester 10
0 parts by weight and 70 parts by weight of ethylene glycol were mixed with calcium acetate and magnesium acetate as transesterification catalysts, and methanol produced as a by-product was distilled out of the system.
The ester exchange reaction was carried out while heating to ℃ C, and at the stage when methanol was almost completely distilled off, germanium acetate was added as a polymerization catalyst, and subsequently trimethyl phosphate was added as a stabilizer to terminate the transesterification reaction. . Next, the reaction product was subjected to a polycondensation reaction under high temperature and high vacuum to obtain a prepolymer having an intrinsic viscosity of 0.55. After making this prepolymer into a strand type chip, it was further subjected to solid phase polymerization under heating and vacuum to obtain a solid phase polymerized polymer having an intrinsic viscosity of 0.65.

2. Bottle molding A preform was injection molded using the stabilizer polymer obtained above, and then the preform was heated and oriented blown to form a bottle. The preform was molded with a M100DM molding machine manufactured by Meiki Seisakusho (cylinder setting 295).
° C, screw rotation speed 120 rpm, molding cycle 35
sec), and the average body thickness of the preform is 4.4 m.
m, and the weight was about 56 g. The bottle is KRUPP COR
Molded with POPLAST LB01, bottle capacity approx.1.0
The average body thickness was 300 μm in 1 (liter).

3. Ultraviolet irradiation and washing The bottle obtained above was irradiated with ultraviolet light, and the portion was washed. At that time, haze was measured after washing and drying.
This operation from ultraviolet irradiation to haze measurement was repeated 15 times.

The ultraviolet irradiation was performed at a ratio shown in Table 2 using a xenon tester; Shimadzu xenon tester XW-150 on the body of the bottle. UV light (310-400n
m) is the MINORUTA UV intensity meter UM-
10 (light receiving unit UM-360).

The cleaning liquid shown in Table 1 was used. The cleaning was carried out by the dipping method under the conditions shown in Table 2, and after the cleaning, it was washed with water.

[0038]

[Table 1]

[0039]

[Table 2]

From Table 2, it can be seen that the bottle is kept transparent by washing with the washing liquids 1 and 2, but the alkaline liquid (washing liquid 3).
It can be seen that the transparency of the bottle deteriorates during washing.

Examples 7 to 9 Production of Polymer A polymer (copolymer) was produced in the same manner as in Example 1 except that the copolymerization components shown in Table 3 were copolymerized.

[0042]

[Table 3]

2. Bottle molding, ultraviolet irradiation and washing A bottle was molded in the same manner as in Example 1 except that the above polymer was used. Furthermore, using this bottle, ultraviolet irradiation and washing were repeated in the same manner as in Example 1 except for the conditions shown in Table 4.

[0044]

[Table 4]

[Embodiments 10 and 11] Embodiments 1 and 5
The sample was sampled at the stage where UV irradiation and washing were performed once, and the amount of methanol and m-xylene adsorbed on the sample was measured. Table 5 shows the results.

[0046]

[Table 5]

[0047]

According to the present invention, a polyester resin container whose surface has been deteriorated by irradiation with ultraviolet light and which is repeatedly used can be washed without lowering the transparency.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Hiroki Nagano 77 Term Kitayoshida-cho, Matsuyama-shi, Ehime Teijin Limited Matsuyama Plant F-term (reference) 3B201 AA22 AB01 BB02 BB82 BB94 CB01 CC01 CC21 4J002 CF081 DH026 EW046 FD036 GG01

Claims (7)

[Claims] When washing a container made of a polyester resin which is used repeatedly, the surface of the container is washed with a warmed aqueous solution of a surfactant whose pH at 25 ° C. satisfies the following formula (1): A method for cleaning a container made of a polyester resin, characterized by cleaning with water or hot water. ## EQU1 ## 6 <pH <8 (1) 2. The method for cleaning a polyester resin container according to claim 1, wherein the haze of the polyester resin container after being repeatedly used 15 times is 15% or less. 3. The surfactant represented by the following formula (2):
2. The method according to claim 1, wherein at least one of (3) and (4) is used.
A method for cleaning a polyester resin container according to the above. Embedded image However, in these formulas, M is Na, K or Ca, and R is C
_{H 3 (CH 2) m CH} 2 -, m is the number of 9 to 28, X is H or -CH ₂ CH ₂ OH. 4. The method for cleaning a polyester resin container according to claim 1, wherein the temperature of the heated aqueous solution is 50 to 100 ° C. 5. The method for cleaning a polyester resin container according to claim 1, wherein the container comprises a polyester resin containing ethylene-2,6-naphthalenedicarboxylate as a main repeating unit. 6. A polyester resin container washed by the method according to claim 1. Description: 7. The polyester resin container according to claim 6, wherein the residual amount of methanol in the container after washing is 3,500 ppm or less, and the residual amount of m-xylene is 100 ppm or less.