JPH0531789A - Manufacture of blown bottle - Google Patents

Abstract

PURPOSE:To enhance transparency and heat shrinkage resistance by a method wherein cold parison, which is produced out of stock polyester having the specified repeating unit, is stretch-blow-molded under the specified conditions. CONSTITUTION:Cold parison, which is made of polyester resin having 80mol.% or more of repeating unit or ester unit consisting of 1,3-propanediol and terephthalic acid or their ester-forming derivatives is blow-molded, resulting in manufacturing a bottle. In this case, the cold parison is stretched by blowing pressure fluid under the heating atmosphereling within the range: Tg-10<=Ta<=Tcc ( deg.C) and, in succession, the resultant parison is heat-set in molds having the temperature range: Tcc<=Tb<=Tm in order to obtain the desired blown bottle, in which Ta is stretching temperature, Tb is the temperature of the molds and Tg, Tcc and Tm represent respectively the glass transition temperature, cold crystallization temperature and melting temperature of resin measured by means of the differential thermal analysis method on JIS K7121 at the temperature rise rate of 10 deg.C/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a blow bottle having excellent transparency and heat shrinkage resistance.

[0002]

2. Description of the Related Art Polyesters, especially polyethylene terephthalate, are excellent in mechanical properties, heat resistance, chemical resistance, gas barrier resistance, etc. and have been conventionally used for fibers, films and the like. Further, it has recently been used for blow bottles used for beverages, foods, cosmetics and the like, and has been attracting attention. As a method for producing these blow bottles, an ink injection blow method, a direct blow method and the like are known. However, polyester blow bottles obtained by the injection blow method, particularly polyethylene terephthalate blow bottles, have inferior impact strength and poor heat shrinkage resistance. Furthermore, although a method has been proposed in which biaxial orientation is sufficiently performed to improve transparency and mechanical strength, the blow bottle obtained by this method is a blow bottle having low heat shrinkage but has low orientation. It has the disadvantage of being inferior to. Further, in recent years, a method of further heat-treating a molded container, a method of raising the temperature of a blowing mold, and the like have been proposed, but these methods improve the heat shrinkage resistance of a polyethylene terephthalate blow bottle, but on the other hand. , A whitening phenomenon occurs due to the progress of crystallization, and transparency is greatly impaired. On the other hand, in the direct blow method, it is required that the molten parison has a high molecular weight capable of retaining the shape, and the container is not so familiar with the low temperature mold, and it is difficult to faithfully reproduce the uneven pattern. As described above, it is difficult to manufacture a blow bottle that sufficiently satisfies all of the properties such as heat shrinkage resistance and transparency, and its realization is earnestly desired in a wide industrial field. An object of the present invention is to provide a method for manufacturing a polyester blow bottle having excellent performance against such problems.

[0003]

As a result of intensive studies made by the present inventors in order to solve the above problems, as a raw material polyester, a polyester containing a specific repeating unit was used, and cold obtained from the polyester was used. The present inventors have completed the present invention by finding that a blow bottle having excellent heat-shrinkability can be provided by maintaining stretchability in a heated atmosphere by stretch blow molding a parison under a specific condition. That is, in the present invention, 80 mol% or more of the repeating unit
In a method for producing a bottle by blow molding a cold parison made of a polyester resin composed of an ester unit of 1,3-propanediol and terephthalic acid or an ester-forming derivative thereof, a cold parison is represented by the following general formula (I): The method for producing a blow bottle is characterized in that a pressurized fluid is blown in under a heating atmosphere in (1) to be stretched, and then heat-set in a mold in the range of the following general formula (II). (I) T _g −10 ≦ T _a <T _cc (° C.) (II) T _cc ≦ T _b ≦ T _m −30 (° C.) (where T _a : stretching temperature, T _b : mold temperature, T _g , T _cc ,
T _m : glass transition temperature of resin measured at a temperature rising rate of 10 ° C./min by a differential thermal analysis method based on JIS K 7121, respectively.
Cold crystallization temperature, melting temperature (° C.)) Raw material compounds necessary for forming the polyester resin used in the present invention will be described below.

First, the raw material compound necessary for forming the terephthaloyl group is terephthalic acid or its ester-forming derivative, and examples of the derivative include those selected from dialkyl esters and diacyl compounds.
Of these, preferred is terephthalic acid or its dialkyl ester, and particularly preferred is dimethyl terephthalate. Further, the diol residue forming the main constituent unit is introduced by using 1,3-propanediol as a monomer raw material. The polyester resin used in the present invention comprises 80% by mole or more of repeating units of an ester unit of 1,3-propanediol and terephthalic acid or its ester-forming derivative, and is produced by using the above-mentioned essential raw material compounds. Includes both polypropylene terephthalate (PPT) homopolyesters and copolyesters incorporating multiple components. As a comonomer raw material for constituting such a copolyester, conventionally known carboxylic acids and derivatives thereof, hydroxycarboxylic acids and derivatives thereof, phenols and derivatives thereof, aliphatic alcohols and derivatives thereof, alicyclic alcohols and derivatives thereof , Amines and their derivatives, hydroxyamines and their derivatives, amides and their derivatives, isocyanates and their derivatives, isocyanurates and their derivatives, and the like, or two or more of them. Specific raw material compounds include dimethyl 2,6-naphthalenedicarboxylate and 2,7-
Dimethyl naphthalene dicarboxylate, dimethyl diphenate, dimethyl 4,4'-diphenyl dicarboxylate, dimethyl adipate, dimethyl sebacate, dimethyl 1,4-cyclohexylene dicarboxylate, ethylene glycol, diethylene glycol, triethylene glycol, 1,4- Butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, 1,4-cyclohexanedimethanol, 1,4-
Cyclohexanediol, p-xylidene glycol,
Dimer diol, hydroquinone ethylene oxide adduct, 2,2-bis (4-hydroxyphenyl) propane ethylene oxide adduct, bis (4-hydroxyphenyl) sulfone ethylene oxide adduct, 2,2
-Bis (3,5-dibromo-4-hydroxyphenyl) propane ethyleneoxy adduct, 2,6-dihydroxynaphthalene ethylene oxide adduct, trimethyl trimesate, trimethyl trimellitate, trimethylolpropane, pentaerythritol, stearyl alcohol , Methyl o-benzoylbenzoate, methyl p-hydroxyethoxyphenylcarboxylate, polytetrahydrofuran, polyethylene glycol and the like. The copolyester of the present invention can contain the comonomer in an amount of 20 mol% or less based on all the constituent units, and preferably
10 mol% or less is good. When the above-mentioned mole fraction is more than 20 mol%, the crystallinity of the blow bottle is deteriorated, the mechanical strength and the heat shrinkage property are impaired, and the whitening phenomenon of the container appears, which is not preferable. These polyester resins can be produced by melt polymerization, solution polymerization, interfacial polycondensation, etc. utilizing conventionally known condensation reaction or transesterification reaction. Further, it is possible to further increase the degree of polymerization by using the solid-phase polymerization method of the obtained resin under reduced pressure or under an inert gas stream. The intrinsic viscosity of the polyester resin of the present invention obtained by such a production method is 25
It is preferably 0.7 or more in orthochlorophenol at 0 ° C. When the intrinsic viscosity is lower than 0.7, molding processability, particularly stretchability is impaired, and the blow bottle has poor impact resistance, which is not preferable.

The polyester resin of the present invention may be supplemented with other thermoplastic resins in a small amount according to the purpose within a range not impairing the effects of the present invention, or a known substance generally added to the thermoplastic resin. For example, stabilizers such as UV absorbers, antistatic agents, flame retardants, flame retardant aids, colorants, lubricants, plasticizers, crystallization accelerators, crystal nucleating agents, fillers, etc. can be added. is there.

The polyester resin of the present invention obtained by such a production method is dried and then subjected to contact quenching with a mold set at a low temperature using a conventional injection molding method to obtain a cold crystal having a low crystallinity. You can get a parison.
The cold parison used in the present invention has a mouth, a shoulder, a body, and a bottom as much as a precursor of a blow bottle, and it is possible to give a tapered shape to the mouth or the shoulder. is there. The limit of the thickness of the cold parison that devitrifies due to crystallization depends on the molecular weight of the resin, the mold temperature, etc., and the molecular weight is high in order to mold a transparent cold parison with a thick wall and low crystallinity. The mold temperature is preferably low, but the thickness of the polyester resin cold parison of the present invention that can be rapidly cooled in a practical injection molding method is 6 mm or less, and particularly preferably 4 mm or less.

In the present invention, the obtained cold parison is subsequently stretched by blowing a pressurized fluid under a heating atmosphere in the range of the following general formula (I), and subsequently in a mold in the range of the following general formula (II). It is characterized by heat fixing inside. (I) T _g −10 ≦ T _a <T _cc (° C.) (II) T _cc ≦ T _b ≦ T _m −30 (° C.) (where T _a : stretching temperature, T _b : mold temperature, T _g , T _cc ,
T _m : glass transition temperature of resin measured at a temperature rising rate of 10 ° C./min by a differential thermal analysis method based on JIS K 7121, respectively.
Cold crystallization temperature, melting temperature (° C.)) The cold parison is stretched and expanded in the circumferential direction using a pressurized fluid such as compressed air or compressed nitrogen within the temperature range of the above general formula (I). At this time, it is also possible to promote axial stretching by using a stretching rod together. The preheating temperature during stretching is T
_{When the} temperature is lower than _g- 10 (° C), the moldability, that is, the stretchability is impaired, the heat-shrinkability and the transparency of the molded container are deteriorated, and the temperature is higher than _Tcc (° C). Uneven thickness of the container after molding occurs and transparency is unfavorable.
Particularly preferably, it is T _g −5 (° C.) or higher and T _cc −2 (° C.) or lower. Further, if the preheating rate during stretching is too high, the production efficiency is increased, but the surface of the cold parison is likely to be whitened, so the preheating time is preferably 30 seconds or more. As a preheating method, a conventionally known heating method is applied, but as a method for uniformly heating the inside of the cold parison, a heating method using a high frequency, a heating method using an infrared heater or a heating method using a far infrared heater is preferable. The preheating may be continuous heating or multi-step heating as long as the general formula (I) is satisfied. The cold parison stretched and expanded using a pressurized fluid in the temperature range of the above general formula (I) is
Then, it is heat set in the mold in the temperature range of the above general formula (II). If the mold temperature is lower than T _cc (℃), the heat setting time will be longer and the blow bottle production efficiency will decrease.
In addition, the heat shrinkage resistance of the container is impaired, which is not preferable. on the other hand,
If the temperature is too close to T _m (° C.), the releasability is deteriorated and partial melting may occur, which is not preferable. Particularly preferred mold temperature range is T _cc +5 (° C) or higher, T _cc +50
(° C.) or lower and T _m −40 (° C.) or lower. Here, the mold temperature can be selected within the temperature range of the above general formula (I) at the mouth, shoulder, body, and bottom of the molded body. The time required for heat setting varies depending on the mold temperature, the thickness of the molding container, etc., but is preferably 2 seconds or more.
Within 30 seconds. It should be noted that a proper time for heat fixation is sufficient if the mold temperature is relatively high, and a relatively short time is required if the mold temperature is relatively low.

In the present invention, to specify the draw ratio of the stretch-blown blow bottle, the draw ratio in the axial direction with respect to the body is 1.5 times or more, and the draw ratio in the circumferential direction is 2 times or more. . Particularly preferred is a draw ratio of 2 or more in the circumferential direction with respect to the body, and a draw ratio of 2.5 or more in the axial direction. Further, the axial stretch ratio with respect to the periphery of the shoulder portion is preferably 1.2 times or more, and the circumferential stretch ratio is preferably 2 times or more.

According to the present invention, the stretch blow molding through the above manufacturing method makes it possible to obtain a blow bottle having excellent heat shrinkage resistance without losing transparency even in a heated atmosphere. On the other hand, when another polyester such as polyethylene terephthalate is used instead of the polyester resin used in the present invention, the stretch blow molding may be performed through the same production method as described in Comparative Examples below. It is difficult to combine these characteristics, and the transparency is particularly lowered.

[0010]

The blow bottle obtained by the present invention is
Since the transparency is not lost even under a heating atmosphere and the heat shrinkage resistance is excellent, the field of application is widely useful as a container used for beverages, foods, cosmetics and the like.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Production Example 1 (Synthesis of Polyester A) 330 parts by weight of dimethyl terephthalate, 258 parts by weight of 1,3-propanediol, and 0.2 parts by weight of titanium tetrabutoxide as a catalyst were reacted with a double helical stirrer and a distillation tube. After being placed in a machine and sufficiently replaced with nitrogen, the temperature was raised to 160 ° C. under normal pressure and stirring was started. Further, the temperature was gradually raised and the by-product methanol was distilled off. When the temperature reached 250 ° C, gradually depressurize the reactor,
Stirring was continued for 3.0 hours at a pressure of 0.1 torr to obtain a polypropylene terephthalate resin (PPT) having an intrinsic viscosity of 0.78 in orthochlorophenol at 25 ° C. The obtained resin was pelletized and subjected to solid phase polymerization at 195 ° C. under a nitrogen stream to obtain a high polymerization degree polyester having an intrinsic viscosity of 1.35. The T _g (glass transition temperature), T _cc (cold crystallization temperature), and T _m (melting temperature) of the obtained resin were measured by a differential thermal analysis method based on JIS K 7121 at a heating rate of 10 ° C./min. . The results are shown in Table 1.

Production Examples 2 to 6 (Synthesis of Polyesters B to F) Ethylene oxide 2 mol adduct of 2,2-bis (4-hydroxyphenyl) propane (polyesters B and C) as a comonomer, bis (4-hydroxyphenyl) A production apparatus similar to that of Production Example 1 was prepared by using a predetermined amount of ethylene oxide 2 mol adduct of sulfone (polyester D), dimethyl 2,6-naphthalenedicarboxylate (polyester E), and 1,4-cyclohexanedimethanol (polyester F). To obtain copolyester. Each of the obtained copolyesters was solid-phase polymerized to obtain a high degree of polymerization polyester. The ratio of 1,3-propylene terephthalate units introduced into polyester was determined by ¹ H-NMR using trifluoroacetic acid-d as a solvent.
It was analyzed by the method. The results are shown in Table 1. The characteristic values of polyester G (polyethylene terephthalate) used in the following comparative examples are also shown.

Examples 1 to 5 and Comparative Examples 1 to 2 Pellets of polyesters A to G were sufficiently dried by heating with a hopper dryer, and then the cylinder temperature was 240 to 270 ° C.
(Comparative Example 2 was 260 to 280 ° C.), a cold parison having an outer diameter of 25 mm, a height of 150 mm and a wall thickness of 20 mm was molded by an injection molding machine having a mold temperature of 25 ° C. The obtained cold parison was transferred to a blow molding machine equipped with an infrared heater, and preheated at the temperatures shown in Table 2 for 50 seconds. Subsequently, compressed air was introduced into the mouth portion of the cold parison while being stretched in the axial direction with a stretching rod to stretch and expand in the circumferential direction, and the stretched cold parison was heat-set for 10 seconds in a mold having a temperature shown in Table 2. Blow bottles were manufactured. The stretch ratio in the axial direction of the obtained blow bottle with respect to the body was 2.2 times, and the draw ratio in the circumferential direction was 4.0 times. Each of the obtained blow bottle bodies is cut out and integrated sphere type HT based on JIS K 7105.
The haze value was measured with an R meter. Next, fill each of the blow bottles with hot water at 90 ° C and let it stand at room temperature for 20 minutes.After that, determine the heat shrinkage ratio from the internal volume before filling and the internal volume after filling, and blow after filling. The body of the bottle was cut out and the haze value was measured. The results are shown in Table 2.

Examples 6 to 9 and Comparative Examples 3 to 5 Blow bottles were produced in the same manner as in Example 1 except that polyester A was blow molded under the molding conditions shown in Table 3.
The same characteristic evaluation as in Example 1 was performed. The results are shown in Table 3.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

Claims (2)

[Claims] 1. A method for producing a bottle by blow molding a cold parison made of a polyester resin, wherein 80 mol% or more of repeating units are composed of ester units of 1,3-propanediol and terephthalic acid or its ester-forming derivative. In the blow, the cold parison is stretched by blowing a pressurized fluid under a heating atmosphere in the range of the following general formula (I), and subsequently heat set in a mold in the range of the following general formula (II). Bottle manufacturing method. (I) T _g −10 ≦ T _a <T _cc (° C.) (II) T _cc ≦ T _b ≦ T _m −30 (° C.) (where T _a : stretching temperature, T _b : mold temperature, T _g , T _cc ,
T _m : glass transition temperature of resin measured at a temperature rising rate of 10 ° C./min by a differential thermal analysis method based on JIS K 7121, respectively.
Cold crystallization temperature, melting temperature (℃)) 2. The method for producing a blow bottle according to claim 1, wherein the polyester resin has an intrinsic viscosity of 0.7 or more.