JPH0321568B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a string-like or plate-like product of polytetramethylene terephthalate-based polyester, and more specifically, a method for producing a string-like or plate-like product made of polytetramethylene terephthalate-based polyester. ,
The present invention relates to a method for producing a string or plate-like product that is easy to take off and has excellent process performance in subsequent steps such as cutting into chips and drying.

Currently, among polyesters, polyethylene terephthalate (abbreviated as PET) is produced in large quantities and used for a wide range of purposes. PET is polymerized in a molten state by a polycondensation reaction, and after the polymerization is completed, it is extruded out of the reactor in a molten state in the form of a string or plate, cooled and solidified by contact with water at room temperature, and then collected.
It is cut into strips (chips) by a cutting machine. At this time, PET chips are obtained in an amorphous state. Thereafter, the chips are heated gradually to crystallize them, and then dried under heat to remove moisture. The dried chips are heated and melted, and then passed through a desired die and melt-molded into fibers, films, or other forms of use to produce products. The present inventors have discovered that polytetramethylene terephthalate (also known as polybutylene terephthalate,
When we investigated the above-mentioned process for PBT polyester (hereinafter abbreviated as PBT), we found that, unexpectedly, good chips could not be obtained in PBT polyester under the same conditions as PET. We have arrived at the present invention by recognizing that this is extremely important. That is, the present invention provides thermoplastic polyester in which 75 mol% or more of the repeating structural units are tetramethylene terephthalate, which is made into a string or plate shape in a heated molten state.
It is characterized in that it is brought into contact with hot water at a temperature of above 70°C and cooled and solidified while generating and growing spherulites. In the present invention, a polyester in which 75 mol% or more of the structural units are tetramethylene terephthalate refers to a polyester containing terephthalic acid and 1,4-butanediol as constituent components.
Up to 25 mol% of the terephthalic acid component is replaced by other dibasic acid components such as aliphatic dibasic acids such as adipic acid and sebacic acid, isophthalic acid, naphthalene dicarboxylic acid, biphenyldicarboboxylic acid, and 1,2-bis( Substituted with one or more aromatic dibasic acid components containing an aromatic ring such as p-carboxyphenoxy)ethane, and/or
25 mol% or less of the butanediol component is other glycol component, polymethylene glycol having 2 to 10 carbon atoms other than 1,4-butanediol,
For example, polymethylene glycols such as ethylene glycol and hexamethylene glycol, polymethylene glycols with alkyl side chains such as neopentyl glycol and hexylene glycol, or diethylene glycol, triethylene glycol, polyethylene oxide glycol, polypropylene oxide glycol, polytetramethylene One or more types of glycol components such as ether glycols such as oxide glycol, alicyclic diols such as 1,4-cyclohexanedimethanol, or glycols having an aromatic ring such as paraxylylene diol and hydroquinone bisglycol ether. It is a crystalline and thermoplastic polyester. Such polyesters of the present invention can be produced by already known reactions such as direct esterification of the corresponding dibasic acid and glycol followed by polycondensation reaction, or transesterification and polycondensation reaction of dibasic acid dialkyl ester and glycol. It may contain compounds known to be added to polyesters, such as catalysts, stabilizers, and pigments.

In the present invention, the string-like or plate-like shape has a diameter or thickness after solidification of 0.7 mm or more and 5 mm or less, preferably 1 mm or more and 4 mm or less, and the length and width are arbitrary. The molten polyester is gradually thinned by drawing, cooling, and crystallization.
Alternatively, since it becomes thinner, it is difficult to specify the size before solidification, but it is preferably several times or more larger than after solidification. In the present invention, the molten polyester is made into a string or plate shape and brought into contact with hot water at a temperature of 30° C. to 70° C. to generate and grow spherulites while being cooled and solidified. The melting point of the target polyester varies depending on the composition of the polyester, but is 130-140°C or higher and 230°C. Therefore, the molten polymer heated above the melting point, preferably 160-270°C, is passed through an appropriate mouthpiece to form a string or plate. extruded into hot water of 30°C or higher and 70°C or lower. The contact method is, for example, introducing the molten polymer into hot water in a tank or gutter installed directly below the nozzle,
Alternatively, a method can be adopted in which hot water is showered directly under the nozzle, and in this case, it is also possible to partially contact a guide or roll to take up the polymer or as an auxiliary means. Official means are used as cold methods. The temperature of the water in contact with the molten polymer is over 30℃
The temperature must be below 70℃. At temperatures below 30°C, spherulite generation and growth do not substantially occur, and the polymer is deformed and solidified, which is not preferable. In other words, a string-like object has a meandering shape and sticks together due to contact between the strings, and a plate-like object has variations in thickness and width, resulting in unevenness. Such deformed products are prone to cutting errors, may get stuck in the blade, or have whisker-like or other protrusions on the cut end of the chip, which significantly impedes subsequent processing. In addition, the occurrence and growth of spherulites are virtually not observed;
Due to the large number of protrusions, sticking is likely to occur, which also hinders subsequent steps.
When the temperature of the water in contact is 30°C or higher, the above-mentioned troubles decrease rapidly, and in particular, when the temperature of the water in contact is 35°C or higher, they are no longer noticeable. For this reason, 80℃ or higher, preferably 35
It is better to use warm water above ℃. At temperatures above 30°C, spherulites occur and grow, the polymer turns white, solidifies in its normal form, and is smoothly cut, without causing any stiction between the polymers before and after the process. Such favorable conditions are maintained even at temperatures above 35°C, and from the viewpoint of the generation and growth of spherulites, a higher temperature of 40°C or above is optimal. However, if the temperature is higher than that, for example 60-70°C, cutting the polymer at that temperature becomes difficult again. In this case, although it is possible to cool the material before cutting, it requires a lot of energy for cooling, which is not a good idea. Therefore, the temperature of hot water is 30℃
A temperature above 70°C is selected. The contact time of the string-like or plate-like polymer with hot water should be the time required for the polymer to whiten and solidify.Although it varies slightly depending on the initial temperature of the polymer, size, composition, hot water temperature, etc., it is approximately 1. It ranges from seconds to 30 seconds. The contact time is not as critical as the hot water temperature selection described above, as long as the polymer whitens and solidifies.

The method of the present invention is applied to PBT and PBT-based copolymers, and its effects are particularly remarkable when the copolymerization ratio is relatively high. The higher the copolymerization ratio, the more severe the above-mentioned drawbacks become and the more difficult the process becomes, but these problems are solved by the method of the present invention. In the case of PET, even if the method of the present invention is applied, the generation and growth of spherulites does not substantially occur, but smooth cutting is possible at room temperature, and no sticking of chips occurs at room temperature. However, during subsequent heating, sticking occurs, so care must be taken to heat the material to crystallize it, and then heat it to dry at a higher temperature before melting and molding. On the other hand, in the case of PBT and PBT-based copolymers, by solidifying the molten polymer while generating and growing spherulites using the method of the present invention, string-like or plate-like objects of normal shape can be obtained, making it easy and reliable to cut into chips. In addition, the chips do not cause thermal aggregation, and can be heat-dried and melt-molded without any special crystallization treatment.

Examples are given below to describe specific implementation methods and effects of the method of the present invention.

Example 1 Using tetraisopropyl titanate as a catalyst,
Dimethyl terephthalate, 1,4-butanediol and 1,6-hexanediol were used to produce poly[(tetramethylene/hexamethylene) terephtate with a butanediol component of 79 mol%, a hexanediol component of 21 mol%, an intrinsic viscosity of 0.95, and a melting point of 198°C. ) was synthesized and the 260
It was extruded into a string shape at ℃, passed through a 10 cm air layer, and then immersed in warm water at a constant temperature. The hot water is in the hot water tank and flows gently in the direction in which the string-like polymer is drawn.
The temperature is maintained at a constant temperature by circulating between the temperature control tank attached to the tank. There are 5 holes with a diameter of 5 mm on the base.
The openings are arranged in a straight line at regular intervals, from which the polymer is extruded downward in five parallel streams. There are two guide rolls that rotate freely in the warm water, and the polymer contacts the first roll and changes its course horizontally through the warm water, then changes its course upward with the second roll and exits the warm water bath. out into the air. It then passes through an adjacent similar cold water bath or without passing through, passes through a take-up roll and is cut into chips by a rotary blade cutter and received in a receiver. When we experimented by changing the hot water temperature and contact time, we found the following results. First, when the temperature of both the hot water bath and the cold water bath was 15°C, the polymer meandered, remained transparent, twisted, and solidified in a curved form. When the meandering was severe, there were cases where the strings came into contact with each other and became stuck. It remained transparent even after contact with water for more than 30 seconds. In addition, although it was possible to cut the chip with the cutting machine, the blade sometimes got stuck and it was necessary to stop the cutting machine to repair it, and many whisker-like protrusions were observed at the end of the chip. Next, when the hot water bath temperature was set to 30℃ and the experiment was repeated without passing through the cold water bath, the polymer began to become thin and white at 2.7 seconds after entering the hot water bath, and while the whiteness increased, the hot water bath was stopped after 6 seconds. It was then transferred to a cutting machine via a pulling machine. There was almost no meandering of the bath water polymer, and the cutting was smooth and chips with a normal shape were obtained. The diameter of the tip is
It was 1.2mm. Furthermore, when the chips were cut into thin sections and observed under a polarizing microscope, spherulites were confirmed, and it was also revealed that the polymer had whitened.
Next, the experiment was repeated with a hot water temperature of 40°C and a cold water bath temperature of 20°C. The polymer began to whiten 2 seconds after entering the hot water bath, and the whiteness increased more clearly and rapidly than at 30°C. Leave the hot water bath after 6 seconds and continue with 2
It passed through a cold water bath for seconds and was transferred from the pulling machine to the cutting machine. No meandering or deformation of the polymer occurred in the bath, and chips with a normal shape were successfully obtained. When these chips were piled up to a height of 50 cm and placed in a hot air dryer at 120°C, they were dried without sticking.

Example 2 Polyester with an intrinsic viscosity number of 0.92 and a melting point of 190°C, consisting of 15 mol% polyethylene oxide glycol component with an average molecular weight of 400, 85 mol% 1,4-butanediol component, and terephthalic acid component as dibasic acid component, was heated at 25°C. After the polymerization was completed, it was taken out from the cap attached to the lower part of the polymerization reactor and the method of Example 1 was repeated. At a hot water bath temperature of 50°C, the polymer is heated after entering the hot water bath.
It started to turn white at 1.5 seconds, and after 6 seconds, I left the hot water bath.
Then, it passed through a cold water bath at 17°C for 2 seconds and was transferred from the pulling machine to the cutting machine. There was no meandering or deformation of the polymer in the bath, and normally shaped chips were successfully obtained. The chips were placed in a vacuum dryer at 120°C and dried without sticking. The dried chips had a diameter of 1.1 mm and a length of 1.0 mm. The dried chips were melted at 230°C in a melt extruder, extruded through a T-die, and solidified on a cooling drum to form a film. Melt extrusion molding into a film went smoothly without any trouble.

For comparison, the method of Example 2 was repeated with the hot water bath temperature set at 17°C, but the polymer meandered in the bath and deformed. Although the collection speed was increased, there were no signs of improvement. The polymer was clear and solidified and could be cut into chips, but it sometimes got stuck in the cutting machine's rotating blade, and the chips had protrusions. When the chips were placed in a vacuum dryer at 120°C, agglutination occurred. For another comparison, when the method of Example 2 was repeated with a hot water temperature of 80°C, the polymer progressed without meandering as in Example 2.
Although it solidified while turning white, the polymer remained warm even after bathing in cold water, and chips that were not cut and were still connected and chips with whisker-like protrusions were found here and there.

Example 3 Terephthalic acid component 92 mol%, adipic acid component 8
mol%, 1,4-butanediol component 89 mol%,
Intrinsic viscosity consisting of 11 mol% polytetramethylene oxide glycol component with average molecular weight 700
0.87, with a melting point of 181℃, after the polymerization reaction is completed, from the slit-shaped nozzle attached to the bottom of the reaction vessel.
It was extruded into a plate shape at 240°C and cast onto a rotating drum.
The upper part of the rotating drum is close to the mouthpiece, and the lower part is immersed in a hot water bath, and the temperature inside the drum is regulated by flowing hot water at the same temperature as the hot water bath. At the point where the molten polymer begins to come into contact with the drum, warm water at the same temperature as the hot water bath is constantly poured onto both sides of the polymer in a plate-like flow. The polymer travels on the drum while being cooled, leaves the drum at or just past the bottom of the drum, travels horizontally through the hot water bath, exits the bath through freely rotating gag guide rolls, and is released from both the top and bottom sides. It passes through a cooling device that showers cold water, passes through a take-up roll, and is transferred to a cutting machine, where it is cut vertically and then horizontally into chips. When the plate-shaped polymer was cooled and solidified at a hot water temperature of 50°C and a cold water temperature of 17°C, the polymer solidified while turning white on contact with the hot water, and chips with a normal shape and a thickness of 1.5 mm were smoothly obtained.

For comparison, when the above method was repeated under the same conditions except for the hot water temperature of 20°C, the polymer solidified while remaining transparent, and the width and thickness were uneven. There were also many cutting errors. Also, sticking occurred when it was placed in a vacuum dryer at 120°C. For another comparison, the polyester obtained in Example 3 was extruded into a string at 240°C through a nozzle attached to the bottom of the reaction vessel, and immediately cut into chips using a cutting machine with a rotating blade in water at 20°C. I did it. This chip
The mixture was transferred to water at 40°C and allowed to stay there for 3 minutes, then dehydrated and dried at 70°C for 30 minutes at normal pressure, and further dried at 95°C for 4 hours at 1.2 Torr. We obtained an oblong chip with a major axis of 3 mm and a minor axis of 2 mm.
Miscuts and stuck chips were mixed in at a proportion of % by weight.

Example 4 Chips of polytetramethylene terephthalate were made in the same manner as in Example 1, using a hot water bath temperature of 50°C and a cold water bath temperature of 20°C. The cold water temperature was 20℃. The polymer turned white in a hot water bath and solidified smoothly, resulting in a normal chip.

Claims (1)

[Claims] 1. When cooling and solidifying a thermoplastic polyester in which 75 mol% or more of the repeating structural units are tetramethylene terephthalate from a molten state to form a string or plate, the molten polyester is made into a string or plate, A method for producing a string-like or plate-like material, which is characterized by contacting hot water of 30°C or higher and 70°C or lower, generating and growing spherulites while cooling and solidifying the product.