JP2003342358A - Manufacturing method of modified polyethylene terephthalate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystallization rate suitable for effectively manufacturing a blow-molded vessel of a bottle or the like. <P>SOLUTION: The modified polyethylene terephthalate having the crystallization rate suitable for selecting the blow-molded vessel of the bottle or the like is obtained by controlling the crystallization rate through changing a flow ratio of a transfer gas to a pellet in a pellet transfer pipe when the pellet of the polyethylene terephthalate is transferred. The crystallization rate necessary for selecting the blow-molded vessel of the bottle or the like is obtained by applying impact to the pellet of the polyethylene terephthalate, and further changing the flow ratio of the transfer gas to the pellet in the pellet transfer pipe. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing modified polyethylene terephthalate, which is suitable as a forming material for hollow molded containers for beverages and the like.

[0002]

BACKGROUND OF THE INVENTION In recent years, various plastic materials have been used as materials for containers filled with liquids such as carbonated beverages, juice, natural water, liquor, teas for various uses, edible oil, liquid seasonings and the like. Among them, polyethylene terephthalate (PET) is widely used as a material for forming hollow molded containers for beverages because it has excellent transparency, gas barrier property, heat resistance and mechanical strength during molding.

Such a hollow molded container is often filled with a heat-sterilized beverage or the like at a high temperature. At this time, the hollow molding container has sufficient heat resistance so as not to cause problems such as clouding of the hollow molding container due to high temperature filling, deformation such as shrinkage and expansion, and deterioration of self-sustainability due to deformation. Is required.

Further, the plastic material forming the hollow molded container for liquid beverage is strongly required to have both heat resistance and transparency. Furthermore, in manufacturing the hollow molded container, it is desired to manufacture at high speed, and a plastic material that can be manufactured with high productivity is required. In order to manufacture a hollow molded container at a high speed, a plastic material is required to have a high heating crystallization rate and a small variation in quality such as a crystallization rate.

That is, if the crystallization speed is too high, the range of preferable molding conditions becomes narrow, and if the quality of the raw material plastics is large, the yield at the time of manufacturing the molded body becomes low. Therefore, it is desirable that the plastic material used for producing the hollow molded body as described above has a crystallization rate suitable for molding efficiency, molding conditions and the like and has a constant quality. Therefore, a method of adjusting the crystallization rate of polyethylene terephthalate is required.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and provides a molded article having a crystallization rate suitable for molding efficiency, molding conditions and the like and having excellent transparency. It is an object of the present invention to provide a method for producing the obtained modified polyethylene terephthalate.

[0007]

SUMMARY OF THE INVENTION A method for producing a modified polyethylene terephthalate according to the present invention is a method for controlling the crystallization rate of polyethylene terephthalate, which comprises a flow rate of a transfer gas in a pellet transfer pipe and / or a transfer gas and pellets. The crystallization rate is controlled by changing the flow rate ratio.

The pellet transfer pipe at this time may be an ordinary pipe, but it is preferable to use it in combination with a method of giving an impact to the pellets because the crystallization speed can be increased and the crystallization speed can be controlled. Examples of the method of applying an impact to the pellet include a method of forming irregularities on the inner surface of the transfer pipe and a method of colliding the pellet with the collision surface.

The modified polyethylene terephthalate used in the present invention is obtained by polymerizing polyethylene terephthalate in a solid state at a temperature higher than the crystallization temperature of polyethylene terephthalate and lower than the melting point, in addition to polycondensation in a molten state. It is preferably (solid-phase polymerized). This modified polyethylene terephthalate may be one that has been subjected to impact after solid phase polymerization, or one that has been subjected to impact and then solid phase polymerization.

The hollow molded article obtained by molding such polyethylene terephthalate has a half-crystallization time of 30 to 100 seconds at 180 ° C. measured by a differential scanning calorimeter. Further, such a hollow molded article has a crystallization temperature of 132 to 160 ° C. at the time of temperature increase measured by a differential scanning calorimeter.

The modified polyethylene terephthalate according to the present invention will be specifically described below. Modified polyethylene terephthalate The modified polyethylene terephthalate of the present invention, when transferring the pellets of polyethylene terephthalate obtained by a conventionally known method, the flow rate of the transfer gas in the pellet transfer pipe and / or the flow ratio of the transfer gas and the pellets. It can be obtained by controlling the crystallization rate by changing it.

As a method of changing the flow velocity of the transfer gas, there are a method of changing the flow rate of the gas flowing through the transfer pipe and a method of partially changing the inner diameter of the transfer pipe. As a method of changing the flow rate of the gas flowing through the transfer pipe, a method of changing the flow rate of the entire transfer pipe, an inlet and an outlet for the transfer gas are provided in the middle of the transfer pipe as shown in FIG. 1, and a portion between the inlet and the outlet is provided. There is a method of partially increasing the flow velocity.

When the flow velocity of the transfer gas is partially changed, the flow velocity may be changed at any place, but it is preferable to perform it at a place where the pellet is impacted as described later because the effect is increased. When the flow rate of the transfer gas is changed for the purpose of controlling the crystallization rate, it is preferable that the difference between before and after the change is 10% or more. If the difference between before and after the change is less than 10%, the change in the crystallization rate may not be clear.

The flow rate when transferring pellets is 3 to 100 m /
Seconds are preferred, and 5-50 m / s are particularly preferred. If the flow rate is too slow, the pellets cannot be transferred, and if the flow rate is too fast, fine powder and drawn string-like polymer increase, which is not preferable.

As a method of changing the flow rate ratio of the transfer gas and the pellet in the pellet transfer pipe, there are a method of changing the flow rate of the transfer gas and a method of changing the flow rate of the pellet. When changing the flow rate ratio of the transfer gas in the pellet transfer pipe and the pellet for the purpose of crystallization speed control, the difference between before and after the change
It is preferably 10% or more. Difference between before and after change is 10
If it is less than%, the change in crystallization rate may not be clear.

Further, the weight ratio (S / G) of the transfer gas and the pellets in the pellet transfer pipe is preferably 0.2 to 30, and particularly preferably 0.3 to 20. If the S / G is too low, the pellet transfer efficiency will be poor, and if the S / G is too high, there is a concern that the pressure loss in the pellet transfer pipe will be high and the pellet flow will be poor, which is not preferable.

The reason why the crystallization speed can be controlled by changing the flow rate ratio of the transfer gas in the pellet transfer pipe and the pellet is considered as follows. Generally, since the number of pellets flowing in the pellet transfer pipe is large, not all pellets are impacted by the method of impacting pellets described below. It is considered that by changing the flow rate ratio of the transfer gas and the pellets in the pellet transfer pipe, the ratio of pellets to be impacted changes, and the overall crystallization speed changes.

Even in a normal pellet transfer pipe, an effect can be obtained by changing the flow velocity of the transfer gas and / or the flow ratio of the transfer gas and the pellet in the pellet transfer pipe, but when used in combination with the method of giving impact to the pellet, It is preferable because the crystallization speed can be controlled and the crystallization speed can be controlled.

As a method of applying an impact to the pellets of polyethylene terephthalate, a method of providing an uneven portion on the inner wall of the pellet transfer pipe, the distance of the pellet transfer pipe and / or
Alternatively, a method of increasing the number of bends and a method of causing the pellets to collide with a flat surface in the middle of the pellet transfer pipe are mentioned.

As a method of providing an uneven portion on the inner wall of the pellet transfer pipe, a method in which a part of the pipe is made into a pipe having unevenness such as a knurling pipe (made by Nippon Aluminum Co., Ltd.) or an eco-flow pipe (made by Special Steel Pipe Co., Ltd.) There may be mentioned a method of giving unevenness by performing sandblasting etc. in advance. The installation location of the pipe with unevenness may be either a straight pipe part or a bent part, but when it is installed on the bent part, both the effect of the pellet colliding with the wall surface and the effect of contacting the unevenness of the wall surface are obtained. Therefore, it is preferable. The elbow portion bent at a right angle is particularly preferable because the collision strength is maximized.

As a method of increasing the distance and / or the number of bends of the pellet transfer pipe, a method of providing a coiled pipe in a part of the pipe as shown in FIG. 2 and a straight pipe of the pipes as shown in FIG. A method of changing the length and / or the number of bends of the pipe by circling the section is mentioned.

As a method of colliding the pellet with a flat surface in the middle of the pellet transfer pipe, a method of installing a container having a flat surface in the middle of the pellet transfer pipe as shown in FIG. 4 and a method of providing a collision plate inside the pipe as shown in FIG. Is mentioned.

The modified polyethylene terephthalate used in the present invention is obtained by polymerizing polyethylene terephthalate in a solid state at a temperature higher than the crystallization temperature of polyethylene terephthalate and lower than the melting point, in addition to polycondensation in a molten state. It is preferably (solid-phase polymerized). This modified polyethylene terephthalate may be one that has been subjected to impact after solid phase polymerization, or one that has been subjected to impact and then solid phase polymerization.

This modified polyethylene terephthalate is
It has an appropriate crystallization rate that enables efficient production of hollow molded containers such as bottles. Specifically, the half-crystallization time (t1 / 2) of a molded product at 180 ° C is 30.
It is -100 seconds, preferably 40-100 seconds. In addition, the crystallization temperature (Tcc) of the molded product when heated is 132 to 160 ° C, preferably 1
40 to 155 ° C.

Next, the polyethylene terephthalate used in the present invention will be described. Polyethylene terephthalate Polyethylene terephthalate used in the present invention comprises a unit derived from terephthalic acid or its ester derivative (eg lower alkyl ester, phenyl ester etc.) and ethylene glycol or its ester derivative (eg monocarboxylic acid ester ethylene oxide etc.). It is made up of guided units.

This polyethylene terephthalate contains, if necessary, 20 units derived from dicarboxylic acids other than terephthalic acid and / or units derived from diols.
It may be contained in an amount of not more than mol%. Specific examples of such dicarboxylic acids other than terephthalic acid include phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, and diphenoxyethanedicarboxylic acid. The units derived from these dicarboxylic acids may be contained in one kind or in two or more kinds, and may be used as an ester derivative.

Specific examples of diols other than ethylene glycol include diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylene glycol, propylene glycol, butanediol, pentanediol, neopentyl glycol, hexamethylene glycol and dodecamethylene. Aliphatics such as glycol and polyethylene glycol; alicyclic diols such as cyclohexanedimethanol; bisphenols; aromatic diols such as hydroquinone. One or two or more units derived from these diol acids may be contained, and may be used as an ester derivative.

Further, the polyethylene terephthalate used in the present invention may have a unit derived from a polyfunctional compound such as trimesic acid, pyromellitic acid, trimethylolethane, trimethylolpropane, trimethylolmethane and pentaerythritol, if necessary. A small amount, for example, 2 mol% or less based on 100 mol% of the dicarboxylic acid component may be contained.

The proportion of diethylene glycol (DEG) units in such polyethylene terephthalate is usually 0.5 to 2.0% by weight, preferably 0.8 to 1.6% by weight, in the polyethylene terephthalate. When the content of the DEG unit is 0.5% by weight or more, the transparency of the bottle body after molding tends to be good. Also, 2.
When it is 0% by weight or less, the heat resistance and the effect of promoting crystallization are good.

As a method of adjusting the proportion of DEG units in polyethylene terephthalate to the above range, in addition to the method of using diethylene glycol as a raw material for polymerization, ethylene glycol as a main raw material is selected by appropriately selecting reaction conditions and additives. A method of adjusting the amount of by-produced diethylene glycol is mentioned. Examples of additives that suppress the formation of DEG include basic compounds, for example, tertiary amines such as triethylamine, quaternary ammonium salts such as tetraethylammonium hydroxide, and alkali metal compounds such as sodium carbonate.

Examples of compounds that accelerate the generation of DEG include inorganic acids such as sulfuric acid and organic acids such as benzoic acid. The intrinsic viscosity (IV) of the polyethylene terephthalate used in the present invention as described above (phenol /
25 in 1,1,2,2-tetrachloroethane mixed solvent
(Measured at 0 ° C.) is usually 0.3 to 2.0 dl / g, preferably 0.5 to 1.5 dl / g, and more preferably 0.7 to
1.2 dl / g, the melting point is usually 210-265 ° C,
It is preferably 220 to 260 ° C, and the glass transition temperature is usually 50 to 120 ° C, preferably 60 to 100 ° C.

The content of the cyclic trimer in the above polyethylene terephthalate, that is, the content of the cyclic trimer of oxyethylene oxyterephthaloyl units is usually 0.5.
It is desirable that the content is not more than wt%, preferably not more than 0.4 wt%. It is preferable to use polyethylene terephthalate having a content of the cyclic trimer of 0.5% by weight or less, because when molding the resin composition, the mold and the like are less likely to be contaminated and the body of the molded body is less likely to be whitened. The content of the cyclic trimer in polyethylene terephthalate can be reduced by, for example, increasing the solid phase polymerization temperature and further increasing the polymerization time.

Further, it is preferable to subject the pellets after the solid-state polymerization to post-treatment with hot water or steam in order to suppress an increase in cyclic trimer which causes a decrease in productivity during injection molding. The post-treatment is usually performed at 40 to 120 ° C., preferably 50 to 110 ° C. for usually 1 minute to 10 hours, preferably 5 minutes to 5 hours. The polyethylene terephthalate used in the present invention is produced from the above-mentioned dicarboxylic acid and diol by a conventionally known method. In the present invention, as such polyethylene terephthalate,
Usually, "raw material polyethylene terephthalate" which is commercially available in the form of pellets is used, but "repropolyethylene terephthalate" (regenerated polyethylene terephthalate) may be used together with the raw material polyethylene terephthalate, if necessary. Specifically, the polyethylene terephthalate may contain "repropolyethylene terephthalate" in an amount of 1 to 50% by weight.

In the present specification, the "raw material polyethylene terephthalate" is produced in the form of pellets from dicarboxylic acid and diol, and is passed through a molding machine in a heat-melted state to pass through a molding machine or a preform or the like. It is a polyethylene terephthalate having no heat history formed in the above. Further, "repropolyethylene terephthalate" is a polyethylene terephthalate (regenerated polyethylene terephthalate) having a heat history in which such raw material polyethylene terephthalate is pelletized by applying heat again to polyethylene terephthalate that has passed through a molding machine at least once in a molten state. Is. In this way, the process of "passing the raw material polyethylene terephthalate through the molding machine in a heating and melting state" is performed by heating and melting the pellets (pellets) made of the raw material polyethylene terephthalate, and shaping the pellet into a desired shape such as a preform or a hollow molding container. Done.

In the present invention, polyethylene terephthalate is used in the form of pellets. The particle size of the polyethylene terephthalate pellets is not particularly limited, but usually 1.0 to
It is in the range of 5.5 mm, preferably 1.0 to 4.0 mm.

[0036]

The method for producing modified polyethylene terephthalate according to the present invention can provide a modified polyethylene terephthalate having an appropriate crystallization rate so that a hollow molded container such as a bottle can be efficiently produced. it can.

[0037]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples. [Measurement method] In the following examples, various physical properties were measured as follows.

Intrinsic viscosity (IV) Phenol / 1,1,2,2-tetrachloroethane mixed solvent (50
/ 50 weight ratio) to prepare a 0.5 g / dl sample solution at 25 ℃
The intrinsic viscosity (IV) was calculated from the melt viscosity measured in Step 1.

Method for producing molded product sample Using polyethylene terephthalate pellets, injection molding was carried out at a cylinder temperature of 275 ° C. and a mold temperature of 10 ° C. to mold a polyethylene terephthalate bottle preform. 10 from the mouth of this preform
A mg sample was cut out and used as a measurement sample.

Semi-crystallization time (t1 / 2) 3 using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer)
The temperature was raised from 0 ° C to 320 ° C / min to 180 ° C, and isothermal crystallization was performed at 180 ° C. The time from the start of the isothermal crystallization until the area of the exothermic peak became half of the entire exothermic peak was defined as the half crystallization time (t1 / 2). Temperature rising crystallization temperature (Tcc) 3 using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer)
The temperature was raised from 0 ° C to 10 ° C / min, and the peak temperature of the exothermic peak generated at that time was defined as the temperature rising crystallization temperature (Tcc).

[0041]

Example 1 Pellets of polyethylene terephthalate having an intrinsic viscosity of 0.76 dl / g were used as a raw material. This pellet was placed in a facility with a device having a collision surface as shown on the left side of Fig. 4 at the end of a transfer pipe with an inner diameter of 43 mm and a total length of 10 m.
Air transportation was performed under the condition that the weight ratio of pellets and air was 2.5 at m / sec. Injection molding was performed using the pellets that had been pneumatically transported to obtain a measurement sample. The half crystallization time t1 / 2 of this sample at 180 ° C. was 66 seconds.

[0042]

Example 2 Pneumatic transportation was carried out in the same manner as in Example 1 except that the weight ratio of pellets to air was 5.0. The half-crystallization time t1 / 2 of the molded product at 180 ° C. was 70 seconds.

[0043]

[Example 3] Example 3 except that the air velocity was 12 m / s
Pneumatic transportation was performed in the same manner as in 1. The half-crystallization time t1 / 2 of the molded product at 180 ° C. was 71 seconds.

[Selection diagram] None

[Brief description of drawings]

1 to 5 show an example of the manufacturing apparatus of the present invention.

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

Continued front page    F term (reference) 4J029 AA03 AB07 AC01 AC02 AD10                       AE01 KH03 KH08

Claims (5)

[Claims] 1. A method for controlling a crystallization rate of polyethylene terephthalate, which comprises changing a flow rate of a transfer gas in a pellet transfer pipe and / or a flow rate ratio of a transfer gas and a pellet. 2. A crystallization rate of polyethylene terephthalate, characterized in that a shock is applied to the pellets in the pellet transfer pipe, and further the flow velocity of the transfer gas and / or the flow ratio of the transfer gas and the pellets in the pellet transfer pipe is changed. Control method. 3. The method according to claim 1, wherein a change range of the flow velocity of the transfer gas and / or the flow ratio of the transfer gas and the pellet in the pellet transfer pipe is 10% or more. 4. A polyethylene terephthalate molded article 180
The method according to claim 1 or 2, wherein the half-crystallization time t1 / 2 (sec) at ° C satisfies the following formula. 30 ≦ t1 / 2 ≦ 100 5. The crystallization temperature Tcc (° C.) of the polyethylene terephthalate molded product at the time of temperature rise satisfies the following formula:
The method according to any one of 1 to 3. 132 ≦ Tcc ≦ 160