JPH01180309A - Method for crystallization of copolymer polyester resin - Google Patents

Abstract

PURPOSE:To enable resin pieces to be crystallized without making them fused each other by soaking polyester resin into the warm water agitated up to the specific linear velocity and raising the temperature up to the proper temperature through a proper velocity. CONSTITUTION:The polyester resin is thrown and soaked into the warm water which is under the state of being agitated up to the linear velocity, at least, above 0.01 times of the sedimentation rate of the polyester resin in warm water, following this, the temperature raising is started while giving linear velocity continuously from the temperature lower 10 deg.C than the glass transferring temperature (Tg) of the drying period of the polyester resin, furthermore, the temperature raising is performed at the velocity not exceeding 100 deg.C per an hour up to the temperature higher at 15 deg.C than the (Tg) for the crystallization. After the resin treated through this manner is taken out of the hot water, lit is sufficiently removed with the moisture by the use of, for instance, a centrifugal dehydrator, and then transferred to the drying process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for crystallizing a copolyester resin. More specifically, the present invention relates to a method for preventing copolymerized polyester resins from fusing together during heat treatment during drying.

BACKGROUND OF THE INVENTION Polyester resins are widely used today because they have excellent physical and chemical properties. When forming a resin, the polymer after the polymerization reaction is discharged from the polymerization reaction tank, solidified and cut to form polymer particles, and then
It is usually subjected to melting and molding processes such as spinning, film forming, extrusion molding, and injection molding. In this case, copolymer particles usually contain 0.2% by weight of water, and if they are melted as is, hydrolysis will occur, resulting in quality deterioration and problems in the molding process. Needs to dry.

However, especially when polyester is copolymerized with a third component,
When drying so-called copolymerized polyesters, the resin particles tend to fuse to each other during drying compared to polyesters, and it is difficult to dry them without care using normal drying methods. One way to solve this problem is, for example, by triblending amorphous silica before drying (Japanese Patent Application Laid-open No. 55-66948@
(Japanese Unexamined Patent Publication No. 11854/1982), a method of crystallizing the resin surface by immersing it in a volatile organic solvent (Japanese Unexamined Patent Publication No. 11854/1982),
1-81433) etc. have been proposed.

L Problems to be Solved by the Invention] However, the above conventional examples have drawbacks such as contamination caused by foreign components during crystallization, time required for removal, and the need for fireproofing and sanitary measures. It wasn't completely satisfying.

[Means for Solving the Problems] The present invention provides a polyester resin having a linear velocity that is at least 0.01 times the average sedimentation velocity of the polyester resin in hot water, and a Tl glass when the polyester resin is dried. The water is immersed at a temperature 10°C or more lower than the water transition temperature (transition temperature), and then heated at a rate not exceeding 100°C per hour to a temperature exceeding 15°C, while continuing to apply a linear velocity to the water. The present invention relates to a method for crystallizing polymerized polyester resin.

In the following, the present invention will be described in further detail.

The copolymerized polyester in the present invention has terephthalic acid as the main acid component and ethylene glycol as the main glycol component, and contains the following acid components and/or
Alternatively, it is a copolymer containing a glycol component, or a mixture or blend of the copolymer and another polymer.

Examples of acid components other than terephthalic acid include isophthalic acid, naphthalene dicarboxylic acid, adipic acid, sebacic acid, and hexahydroxyterephthalic acid, and the copolymerized amount thereof is usually 0 to 40 mol%. Glycol components other than ethylene glycol include neopentyl glycol,
trimethylene glycol, tetramethylene glycol,
Examples include cyclohexane dimetatool and polyethylene glycol, and the amount of copolymerization thereof is usually 0 to 40 mol%. The present invention is particularly effective for isophthalic acid copolymerized polyesters, and the copolymerization rate thereof is 40 mol% or less, preferably 10 to 30 mol%, more preferably 15 to 25 mol%.
It is. In addition, polyfunctional compounds such as trimesic acid and trimethylolpropane may be used as the acid component and glycol component of the copolyester.

The above copolyester contains pigments such as silica, titanium oxide, kaolin, talc, and calcium carbonate, fillers, as well as weather resistance improvers, optical brighteners, antistatic agents, thickeners, flame retardants, and others. Good too.

Further, the shape of the polyester resin is not particularly limited, and it may be any shape as long as it is a molded product formed into powder, flakes, granules, etc., or a mixture of these. Good too.

The glass transition temperature To in the present invention is determined by drying the polyester resin in hot air at 40° C. for 24 hours so that the moisture content becomes 0.2% or less, and then measuring it with a DSC (differential scanning calorimeter). Desired.

In order to achieve the object of the present invention, it is necessary to start increasing the temperature at a temperature that is 10° C. or more lower than TQ. 10℃ below Tg
If the temperature rise is started from a temperature higher than the lower temperature, the polyester resins will fuse together in the hot water immediately after the start, which is not preferable. If the temperature is too low, it takes a long time to raise the temperature, resulting in a long operation time. Here, 10 to 40°C, more preferably 20 to 3
It is preferable to raise the temperature from a temperature lower than 0°C.

Furthermore, for crystallization, it is necessary to raise the temperature to a temperature higher than TCI by 15°C or more, and preferably to a temperature higher than To by 20°C or more. warm water to 100℃
If the temperature is raised above this level, a pressurizing device is required, but the processing time can be shortened, which is preferable. If the temperature is increased to 160° C. or higher, the polyester resin will deteriorate significantly due to hydrolysis, which is not preferable. The polyester resin must be stirred into warm water at a linear velocity that is at least 0.01 times the sedimentation velocity of the polyester resin in the warm water. If polyester resin is poured into warm water where the linear velocity of water is slower than this, the resin will settle at the bottom of the device and weak fusion will occur, and furthermore, the time that the resins will be in contact with each other will be longer, resulting in a lower temperature during the subsequent temperature rise or This is undesirable because the fusion will be carried over during the treatment period.

More preferably, it is preferable to provide a linear velocity of 0.10 times or more the sedimentation velocity. Note that it is not preferable to apply a linear velocity of five times or more because it increases the size and complexity of the apparatus. The sedimentation rate here refers to the average sedimentation rate when the resin is placed in still warm water. Any method that gives the linear velocity to the water can be used. For example, methods using rotating stirring blades, methods using blowing air, nitrogen gas, etc. from below, etc. can be considered.
It is necessary to design the system so that the total amount of hot water and resin can be applied at linear velocity.

If there is a dead space where the water is not given a linear velocity, the resin will stick and cause fusion.

Roughly speaking, it is necessary to raise the temperature at a rate not exceeding 100°C per hour. If the temperature is increased at a rate exceeding 100° C. per hour, the crystallization of the polyester resin will not follow, resulting in fusion in hot water. Preferably, it is desirable to raise the temperature at a rate of 30 to 80°C per hour. If the heating rate is particularly slow, the purpose of crystallization can be achieved, but the equipment will be used for a long time, which is not economical. After the temperature is raised, the temperature may be maintained at the reached temperature within a range that does not significantly deteriorate the quality of the resin.

After the resin treated under the above-mentioned conditions is taken out of the hot water and water is sufficiently removed using an appropriate method, for example, a centrifugal dehydrator, it can be subjected to a drying process.

The drying method is not particularly limited and a conventional method can be used. Drying is usually carried out below the contact point of the resin, but specific drying methods include blowing hot air at 70 to 200°C into a dryer, blowing hot air into a fluidized bed of resin, or drying at a temperature of 70 to 200°C. This is done by heating the product to ℃ and drying while reducing the pressure inside the dryer.

[Examples] The present invention will be explained in more detail with reference to Examples and Comparative Examples below. Note that parts in the examples are parts by weight, and the method for measuring stirring characteristics is as follows.

A. Polymer intrinsic viscosity (IV) After drying the polyester resin at 105°C for 20 minutes, the 0-
Measurement was carried out at 25°C using chlorophenol as a solvent.

B. TO (glass transition point) of the polymer After drying the polyester resin in hot air at 40°C for 24 hours until the moisture content becomes 0.2% or less, the polyester resin was dried using a DSC (differential scanning calorimeter, manufactured by PerkinElmer) for 24 hours. -2 type), the temperature was raised at 15°C/min under a nitrogen seal, and the temperature was increased to 70°C.
The median value of the endothermic peak near °C was defined as TQ.

Average sedimentation speed of C9 resin A glass cylinder with a diameter of 5C11 and a height of 1 TrL was filled with water at 25° C., and the resin was dropped one by one to determine the average sedimentation speed.

D. Snow melting rate during pre-crystallization The pre-crystallized chips were taken out and the fusion rate was calculated based on the following formula.

Fusion rate during preliminary crystallization - Weight of chip with two or more particles attached xio.

There is virtually no problem if the fusion rate during preliminary crystallization of the total weight of the treated chips is within 2%.

Example 1 5 in which 20 mol% of isophthalic acid was copolymerized based on the total acid components
100 parts of a polyethylene terephthalate/isophthalate copolymer resin having a cubic TO size of 72°C and a size of 5x5x2m was stirred at 56°C with a stirring blade at the bottom at ioorpm.
It was immersed in 200 parts of warm water. The sedimentation rate of the resin at this time was 10 cal and 1 second. The linear velocity of water is 1,0 cll/s
ec, which was 0.10 times the resin sedimentation rate.

While stirring continuously, the temperature was raised to 95°C in 1 hour (heating rate 4
5℃/hour), a bond held for 1 hour after reaching 9b℃,
The hot water was discharged, and then the resin was taken out and dehydrated using a centrifugal dehydrator.

This resin was placed in a rotary dryer and dried for 2 hours at 160°C to 180°C under reduced pressure below 2m1-IQ, but no fusion was observed between the resins or between the resin and the inner wall of the dryer. Ta.

Example 2 When only the heating start temperature was set to 60°C under the same conditions as in Example 1, the fusion rate during the crystallization process was 1.2%, but no a-adhesion was observed during the main drying. There wasn't.

Example 3 Under the same conditions as Example 1, only the temperature increase rate was 95° C./hour, and the fusion during the preliminary crystallization treatment was 1.8%. Note that no fusion was observed during the main drying.

Example 4 Under the same conditions as in Example 1, only the linear velocity of water was set to 0°5 bacteria/second, and the fusion rate during the preliminary crystallization treatment was 0.2%. Note that no fusion was observed during the main drying.

Example 5 Under the same conditions as in Example 1, the temperature after the temperature increase was 120°C and the holding time after the temperature increase was 30 minutes. There was no fusion of crystallization and no fusion was observed during the main drying. Ta.

Comparative Example 1 When water was not subjected to linear velocity under the same conditions as in Example 1, the fusion rate during crystallization was 53%, and it could not be used for main drying.

Comparative Example 2 When the same conditions as Example 1 were used, with only the heating start temperature set to 65° C., 30% fusion occurred during crystallization and the resin could not be subjected to main drying.

Comparative Example 3 When the temperature after heating was 85°C under the same conditions as Example 1 and the holding time after heating was 100 minutes, the fusion rate during crystallization was 0.2%. However, when this resin piece was subjected to main drying, adhesion occurred between the resin pieces and between the resin piece and the wall of the drying unit.

Comparative Example 4 When the heating rate was set to 120° C./hour under the same conditions as in Example 1, 75% fusion occurred during crystallization, and the resin could not be subjected to main drying.

Example 6 5 mol% diethylene glycol was copolymerized as a copolymerization component, and 11 copolymerized polyester resin test specimens were prepared at 7077°C in the same manner as in Example 1, and pre-crystallization treatment was performed (linear sedimentation velocity 15 cM seconds). . The results are shown in Table 1.

Example Example 1 except that the copolymerized amount of fisophthalic acid was 5 mol%.
Copolymerized polyester resin specimens were produced at 7075°C in the same manner as above, and pre-crystallization treatment was performed (sedimentation linear velocity 10
C1a/sec). The results are shown in Table 1.

[Effects of invention The crystallization method according to the present invention has the following effects.

(1) Since it is possible to crystallize the resin pieces without mutually fusing them, handling in subsequent film forming, spinning, etc. is good.

(2) It is economical because it does not require special chemicals and treats hot water.

(3) Since it can be treated using only hot water, there is no contamination with treatment media.

(4) Since no organic solvents are used, it is safe and there are no problems with disposal of waste liquid.

Claims (1)

[Claims] Immersing a polyester resin in hot water having a linear velocity that is at least 0.01 times the average sedimentation velocity of the polyester resin in hot water and at a temperature that is 10°C or more lower than the dry Tg (glass transition temperature) of the polyester resin. A method for crystallizing a copolyester resin, which comprises raising the temperature of water at a rate not exceeding 100° C. per hour to a temperature exceeding 15° C. above the Tg while subsequently applying a linear velocity to the water.