JP2747149B2 - Method for producing polybutylene terephthalate copolymer pellets for molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a polybutylene terephthalate (PBT) copolymer for molding or a pellet thereof comprising a melt-kneaded pellet formed by melt polymerization or compounding using an extruder or the like. PBT copolymer or composition pellets for molding, which flow smoothly without causing cohesion, agglomeration, etc. (hereinafter referred to as sticking) even under high temperature and high load during handling up to molding For the preparation of

[0002]

2. Description of the Related Art In general, resin pellets for molding are produced by melt-kneading a resin or a composition thereof in a reactor or an extruder, extruding them into strands from the pores of a die, and cooling. Solidified through a water bath and cut into pellets for molding, or immediately after extrusion, cut with a rotary blade on the die surface, immersed in water as granules, cooled, dehydrated and provided for molding. In any case, it is general to cool the molten resin in water in any case, but the resin temperature or immersion time during this period, and further the subsequent processing, etc., do not need to be strictly controlled. The emphasis is also placed on workability, and it is common sense and common practice to cool the resin temperature to about 80 ° C or less in a short time and temporarily store it in a storage tank. In the case of polybutylene terephthalate (PBT), the pellets for molding can be prepared by the general method as described above, and the cohesion between the particles during the subsequent handling such as drying can be performed without taking special measures. It can be handled smoothly without inconveniences such as aggregation and aggregation. However, in the case of a PBT-based polyester or a PBT copolymer or a composition thereof, pellets prepared by such a general method are extremely susceptible to sticking in subsequent handling. For example, when pellets are pre-dried for molding or the like, Sticking occurs and the fluidity of the particles deteriorates. For example, a bridge is formed by a hopper dryer of a molding machine. In an extreme case, the flow of the particles is stopped by agglomeration in the shape of an "office" and the supply to the molding machine is stopped. This causes inconveniences such as the occurrence of a problem, and causes considerable trouble in the molding operation. Such a phenomenon is particularly noticeable in high-temperature hoppers used in drying machines and molding, since polyester-based resins generally require preheating or pre-drying before molding. This is an important problem in terms of molding work efficiency and equipment, such as requiring vibration and stirring. Further, even at a relatively low temperature, this phenomenon occurs under a load-applied condition such as accumulation by a pellet bag or storage in a silo, which often causes problems in operation. The sticking phenomenon of the PBT copolymer pellets is such that when the pellets are prepared, the surface is softened and fused due to internal heat when the pellets are deposited in a receiving tank or the like, when the pellets are cooled relatively slowly to keep the pellet temperature relatively high. Sticking occurs, which becomes a problem in handling, and also enhances cooling during pellet preparation and solidifies sufficiently to produce low-temperature pellets.
Subsequent high-temperature treatment such as drying causes sticking, which again has a problem in work. The present invention eliminates the sticking phenomenon of the molding pellets made of the PBT copolymer or the composition thereof, and flows smoothly during pellet preparation, molding, and other handling, and has good workability. It is intended to produce polymer or its composition pellets.

[0003]

Means for Solving the Problems The present inventors have solved such problems of PBT copolymer or pellets of the composition thereof,
As a result of studying to obtain pellets that always flow smoothly without agglomeration during handling during storage, drying, etc. during pellet preparation and have no inconvenience in handling, in order to avoid surface softening and fusion due to residual heat immediately after pellet preparation It is necessary to enhance the cooling to temporarily lower the resin temperature to a specific temperature or less. On the other hand, the PBT copolymer which is the object of the present invention is inherently crystalline, but the crystallization rate of the PBT copolymer is reduced due to its structure. As compared to the above, the pellets, which promoted cooling and solidification and had a low temperature, hardly proceeded with crystallization as described above, and especially the surface thereof was in an amorphous state. In this case, it was confirmed that the heat of crystallization caused aggregation between the particles, and that the once crystallized PBT copolymer pellets did not aggregate even if the pellets were kept at a high temperature again. Temperature etc. Result of pursuing, to reach the present invention,
This has led to the solution of the sticking phenomenon during the preparation of the PBT copolymer pellets and subsequent handling. That is, the present invention mainly comprises a polybutylene terephthalate copolymer or a polybutylene terephthalate copolymer in which 60 to 99 mol% of the repeating structural units are composed of butylene terephthalate groups and 40 to 1 mol% are composed of other repeating structural units. Upon preparing a molding pellet by cooling and solidifying the composition as a resin component from a molten state, extruding the molten polybutylene terephthalate copolymer or a composition thereof,
(a) After cooling and solidifying, the resin temperature is once cooled to below the glass transition temperature (T _g ) of the resin, and (b) it is then cooled above the cold crystallization temperature (T _cc ) of the resin, and The present invention relates to a method for producing polybutylene terephthalate copolymer pellets for molding, which does not cause cohesion of pellets, which is characterized by performing a heat treatment at a temperature lower by 30 ° C.

[0004] As described above, the pellet preparation method of the present invention comprises:
First temperature sufficient that the surface is not fused by self heat, namely a first step of cooling to below T _g (a), followed by a second step to sufficiently crystallized, i.e. heated at T _cc or more temperature It is characterized by comprising two steps of the step (b) of processing.

First, as a first step (a), it is necessary to cool the melt-extruded strands or pellets to below the glass transition temperature (T _g ) of the resin. If the cooling is not sufficient, even if the surface of the pellet is once solidified, if the pellet is deposited on a receiving tank or the like, the surface softens and adheres again, which is not preferable. The cooling is carried out by contacting a time sufficient to below T _g the temperature of the medium of at least the resin and the extruded molten resin. A water bath is preferred as the medium,
The immersion time differs depending on the medium temperature. A short time is sufficient if the medium temperature is low, and a long time is required if the medium temperature is relatively high. In short, it is necessary to cool the resin temperature to _Tg or lower, and in order to perform this in a short time, it is naturally preferable to perform the first-stage solidification cooling in a medium having a low temperature. Generally 3 ° C. than the T _g of the resin in the case of the water bath
It is desirable to pass through a medium (water bath), preferably at 5 ° C. or lower.

[0006] In the case of the PBT copolymer which is the object of the present invention, the pellets which have been sufficiently cooled and solidified in the first step (a) do not reach the original equilibrium crystalline state and are almost amorphous. When the temperature rises above the cold crystallization temperature due to drying or the like in this state, crystallization occurs. At that time, sticking particularly occurs in the stationary deposition state. Therefore, in the second step (b), a process for positively completing such crystallization is performed. This can be achieved by heating the pellets cooled in the first step (a) at least at a temperature higher than the cold crystallization temperature (T _cc ) of the resin for a time sufficient for crystallization. The processing temperature for this is higher than the cold crystallization temperature of the resin and lower than the melting point of the resin by 30 ° C. or less. The higher the temperature, the shorter the required time is, but if the temperature is too high, local heat fusion occurs. It is not preferable because it may occur. As a heating medium for crystallization, a gas such as air or nitrogen or a liquid such as a water bath can be used, but a water bath is generally desirable in terms of heat capacity and temperature uniformity. Cold crystallization temperature
In the case of a resin of 100 ° C. or higher, it is desirable to use air (hot air) or steam. If the crystallization treatment (b) is performed in a stationary state, sticking will occur in the treatment itself and it may become difficult to take out the crystallization treatment. Therefore, it is preferable to perform the crystallization treatment under conditions of flow, stirring, vibration, etc. Processing can be performed more uniformly in a shorter time than when performed inside. If the temperature is relatively high in the above temperature range, the processing time can be shortened. These conditions may be determined as appropriate in consideration of processing equipment, economy, and the like.

Incidentally, the glass transition temperature T of the PBT copolymer or its composition, which serves as a guide for the conditions for carrying out the present invention, is given.
_g , the cold crystallization temperature T _cc , the melting point T _{m and the} like can be determined by measuring at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). According to DSC, peaks or knicks occur in the order of T _g , T _cc , and T _m by increasing the temperature. For example 30 mol% of all the structural units as a copolymer component is T _g 28 ° C. in PBT copolymer having a butylene isophthalate unit, T _cc 59 ℃, a T _m 170 ° C., also of 20 mole% of all the structural units For a PBT copolymer having diethoxybisphenol A terephthalate unit, T _g 46 ° C., T _cc
90 ° C., T _m 185 ° C.

The crystallization step (b) according to the present invention comprises:
Once cooled in a first step (a) the pellets below T _g, immediately performed may be also once after treatment (a), was left to T _cc temperature below the crystallization process timely (b) May be performed,
If the temperature rises carelessly during this time, agglomeration may occur. Therefore, it is preferable to perform the steps (a) and (b) continuously.

The PBT copolymer which is the object of the present invention is:
Terephthalic acid or its ester-forming compound and butanediol as main constituents, and another carboxylic acid or its ester-forming compound or another diol component as a copolymerization component, a butylene terephthalate group 99-60 obtained by a polycondensation reaction. The effect is particularly large when the mole ratio of the PBT copolymer is 95 to 65 mole%. Although such a PBT copolymer is inherently crystalline, its crystallization rate is extremely slow as compared with PBT itself, and crystallization hardly progresses in a normal pellet preparation method. The method of the present invention is effective for causing adhesion. Such a pellet preparation method is effective not only for the PBT copolymer but also for a resin having a low crystallization rate. The copolymer component of the PBT copolymer targeted by the present invention is not particularly limited, and is effective for a PBT copolymer containing a generally known copolymer component. As an example of such a copolymer component, examples of the acid component include aromatic carboxylic acids such as isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, trimesic acid, trimellitic acid, and pyromellitic acid, or adipic acid, azelaic acid, and sebacic acid. Acid, dodecane diacid, saturated aliphatic dicarboxylic acid such as dimer acid, itaconic acid, fumaric acid, maleic acid, or one or two or more carboxylic acids such as long-chain unsaturated dicarboxylic acid or an ester-forming compound thereof. Can be used. Also, as the diol component,
For example, ethylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,8-octanediol, 1,
Aliphatic diols such as 10-decanediol or 1,4-
Cyclohexane dimethanol, bisphenol A, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, bisphenol S and its alkylene oxide adduct, at least a diol component such as naphthalene diol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol One or more types may be mentioned. Further, a hydroxycarboxylic acid such as hydroxybenzoic acid and hydroxynaphthoic acid or an ester-forming compound thereof can also be used as a copolymerization component. The copolymer component may have a halogen substituent.

The pellet preparation method of the present invention is also applicable to the case where the above-mentioned PBT copolymer is taken out of the reactor after melt polycondensation and pelletized, and the PBT copolymer and other thermoplastic resins, Also in the case of preparing pellets of a composition melt-kneaded with an inorganic filler, it is effectively applied to prevent sticking of the pellets. However thermoplastic Te and PBT copolymer itself by its presence at the resin composition _{containing, T g, T cc, T} m value slightly changes pellet preparation conditions since such need to be modified accordingly There is,
When a small amount of other thermoplastic resin is added as a supplement, the value of the PBT copolymer may be approximately used as a guide.

[0011] As the thermoplastic resin to be used supplementarily,
For example, an aromatic polyester resin composed of an aromatic dicarboxylic acid and a diol such as polyethylene terephthalate and polybutylene terephthalate, nylon 6, nylon 6-6
Polyamide resins such as nylon 6-10, nylon 12, nylon 46, olefin resins mainly containing ethylene, propylene, butene, etc., styrene resins such as polystyrene, polystyrene-acrylonitrile, ABS, polycarbonate, polyphenylene oxide, Examples include polyalkyl acrylate, polyacetal, polysulfone, polyethersulfone, polyetherimide, polyetherketone, and fluororesin. These thermoplastic resins can be used as a mixture of two or more kinds.

[0012]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited thereto.

Examples 1 to 14 and Comparative Examples 1 to 6 Dimethyl terephthalate (DMT) and dimethyl isophthalate (DMI) (at a molar ratio of 70:30) were used as acid components.
A melt polycondensation reaction was carried out using -butanediol as a diol component to prepare a PBT copolymer (DMI copolymer units: about 30 mol%). This molten resin is extruded from a die provided at the bottom of the reactor, taken out into the water as a number of strands, immediately cut with a cutter, stored in a receiver, and at the same time a thermometer is inserted into the pellets of the receiver to measure the pellet temperature. One day later, the pellets were examined for sticking. The conditions for preparing the pellets are shown in Table 1a. Next, the pellets which did not cause sticking are shown in Table 1.
The heat treatment was performed under the conditions shown in b above, and the sticking state of the processed pellets was evaluated by the following method. The results are shown in Table 1. The T _{g of} the PBT copolymer used here,
T _cc and T _m were 28 ° C., 59 ° C. and 170 ° C., respectively. Note that T
_The methods for measuring _g , T _cc and T _{m and} the method for evaluating the sticking state are as follows. (1) Measurement of T _g , T _cc and T _m by DSC Using Perkin Elmer DSC-7, about 10 mg of a sample was set, and the temperature was raised at a rate of 10 ° C./min.
_g ), cold crystallization temperature (T _cc ) and melting point T _m were determined. (2) Measurement of pellet temperature The strand from the water bath was cut, immediately received in a cylindrical plastic receiver having a diameter of about 20 cm and a height of about 35 cm, and a thermometer was inserted almost at the center to measure the temperature. . (3) Evaluation of sticking phenomenon 3-1. Judgment of sticking phenomenon immediately after pelletization (a) The above cylindrical receiver (filled with pellets to a height of about 30 cm)
After standing overnight, it was gently knocked down and the state of the pellet was observed. When sticking does not occur, the individual pellet particles separate and flow smoothly, but when sticking occurs, the resin pellets adhere at least partially in a lump, and when severe, the pellets flow at all. Without being solidified into a cylindrical shape. 3-2. Evaluation of sticking phenomenon after heat treatment (b) Put the test pellets (after heat treatment) up to the top of a 200 cc stainless steel beaker, leave them at 100 ° C for 5 hours, and gradually turn the beaker upside down. The pellet was brought down to a certain state, lifted slowly, and the state of sticking of the pellet was observed to determine the presence or absence of sticking. Also in this case, when the sticking phenomenon occurs, the pellets adhere to each other as shown in FIG. 1 and at least a part does not collapse, whereas when the sticking phenomenon does not occur, the pellets do not adhere as shown in FIG. Flows and no agglomerates are observed. It should be noted that this simple determination method has been confirmed to have a very good correlation with sticking with a hopper dryer during actual molding.

[0014]

[Table 1]

Examples 15 to 21, Comparative Examples 7 to 12 Dimethyl terephthalate (DMT) was used as an acid component,
-Butanediol and diethoxybisphenol A (EB
PA) (mol ratio: 80:20) as a diol component to carry out a melt polycondensation reaction to obtain a PBT copolymer (about EBPA copolymer units).
20 mol%). This molten resin is extruded from a die provided in the lower part of the reactor, taken out into the water as a number of strands, immediately cut with a cutter and stored in a receiver, and at the same time, a thermometer is inserted into the center of the deposited pellets of the receiver and the pellet temperature is increased. Was measured, and the presence or absence of sticking of the pellet was examined after one day. The conditions for preparing the pellets at this time are shown in Table 2a. Next, the pellets in which sticking did not occur were heat-treated under the conditions shown in Table 2b, and the sticking properties of the treated pellets were evaluated by the method described in 3-2. The results are shown in Table 2. P used here
The T _g , T _cc and T _m of the BT copolymer were 46 ° C. and 90 ° C., respectively.
° C and 185 ° C.

[0016]

[Table 2]

Examples 22 to 29, Comparative Examples 13 to 17 A 30 mol% isophthalic acid copolymerized polybutylene terephthalate resin and a polycarbonate resin were previously blended at a weight ratio of 85:15, and the cylinder temperature was adjusted to 260 ° C. using an extruder.
Melt and kneaded at ℃, extruded into water as a strand from the die pores, cut immediately with a cutter and stored in a receiver, at the same time insert a thermometer in the center of the deposited pellets of the receiver, measure the pellet temperature, after one day and night The pellets were examined for sticking. The preparation conditions of the pellets at this time are shown in Table 3a. Next, the pellets that did not cause sticking were heat-treated under the conditions shown in Table 3b. Table 3 also shows the results of evaluating the sticking state of the treated pellets by the method described in 3-2. T _g of the PBT copolymer composition used here, T _cc, T _m are each 36 ℃, 75 ℃, it was 170 ° C..

[0018]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a diagram showing a sticking phenomenon after a sticking test of a pellet (Comparative Example).

FIG. 2 is a diagram showing a sticking phenomenon after a sticking test of a pellet (Example).

Claims (2)

(57) [Claims] 1. A polybutylene terephthalate copolymer or a polybutylene terephthalate copolymer comprising 60 to 99 mol% of a repeating structural unit and 40 to 1 mol% of another repeating structural unit. Upon preparing a molding pellet by cooling and solidifying the composition as a resin component from a molten state, extruding the molten polybutylene terephthalate copolymer or a composition thereof, (a)
After cooling and solidifying, the temperature of the resin is once cooled to below the glass transition temperature (T _g ) of the resin, and (b) it is then cooled to the cold crystallization temperature (T _cc ) of the resin and 30 ° C. lower than the melting point. A method for producing a polybutylene terephthalate copolymer pellet for molding, which does not cause cohesion of the pellet, wherein the pellet is heat-treated within a temperature range. 2. The method for producing polybutylene terephthalate copolymer pellets for molding according to claim 1, wherein the steps (a) and (b) are performed in a water bath.