JP5122919B2 - Copolyester resin pellet and method for producing the same - Google Patents

Description

  The present invention mainly comprises a copolymerized polyester resin having a glass transition point (hereinafter referred to as Tg) of less than 40 ° C. that can prevent cohesion of the copolymerized polyester resin pellets (hereinafter referred to as blocking) and can be stored for a long period of time. The present invention relates to pellets and manufacturing methods thereof.

  In general, a thermoplastic resin is melt-extruded from a strand and then cut into resin pellets. Among them, the copolyester resin having a low Tg has high adhesiveness, and the pelletizer using a normal rotating tooth has deteriorated operability, for example, resin pellets adhere to the rotating tooth and the rotation stops. Even if the resin pellets can be cut without any problem, when the resin pellets are stored at room temperature, the pellets are blocked due to the adhesiveness of the resin pellets, and it is necessary to store the resin pellets at a low temperature to prevent blocking. It was.

As a method for preventing the blocking of the copolyester resin having a low Tg, it has been practiced to avoid the pelletization, to pay out in a sheet form, and to use a release film such as a polyethylene film to suppress blocking (patent) Reference 1). However, in the case of sheet-like products, the polyethylene film must be peeled off at the time of use, which is not only economical and time-consuming. In addition, when it is dissolved in a highly flammable solvent, static electricity is generated when it is peeled off. Therefore, there is a possibility of igniting the solvent, which is a big safety problem.

  For such problems, a method of preventing blocking by applying an aqueous dispersion using a polyester resin having a high Tg to a pelletized copolyester resin, forming an aqueous dispersion film on the pellet surface, and drying. (Patent Document 2, Patent Document 3). However, in these methods, when an aqueous dispersion having a high solid content is dried, the powder may agglomerate and the anti-blocking effect may be incomplete, and the powder used when dissolved in a solvent is used. In some cases, the powder precipitated and the solution stability was very poor.

Further, the inventor has proposed that finely divided copolymerized polyester having a glass transition point of 40 ° C. or higher is attached to the periphery of the pellet, and the pellet is covered with an organic compound powder to prevent blocking (Patent Document 4). However, in order to prevent blocking by coating the organic compound powder, it is necessary to make the organic compound a particle size of about 100 μm or less.
JP 2004-300285 A JP 2007-070539 A JP 2007-070540 A Japanese Patent Application No. 2007-089881

  The problem to be solved by the present invention is to effectively prevent blocking of pellets mainly composed of a poorly crystalline copolyester resin having a high Tg of less than 40 ° C. and to block for a long period of time. Furthermore, another object of the present invention is to provide a copolymerized polyester resin pellet having good solution stability even when dissolved in a general-purpose solvent, and a method for producing the same.

  As a result of intensive research in order to solve the above-mentioned problems, the present inventor has made a copolymer polyester resin having a Tg higher than that of the core layer as a sheath layer and a resin pellet in which the core layer is covered with the sheath layer. The present inventors have found that a copolymerized polyester resin solution that suppresses blocking between pellets, can be dissolved in a general-purpose solvent, and has excellent stability can be obtained.

That is, the gist of the present invention is as follows.
(1) Melting a core-sheath type strand having a poor crystalline copolyester resin having a glass transition point of less than 40 ° C. as a core layer and a poor crystalline copolyester resin having a glass transition point of 40 ° C. or more as a sheath layer Extruded, using circulating water added so that the resin solid content of an aqueous dispersion of polyester resin having a glass transition point of 40 ° C. or higher as a cooling medium is 0.1 to 5% by mass, and cooling the strands, into pellets A method for producing a core-sheath copolymer polyester resin pellet, characterized by cutting.

  The copolyester resin pellets of the present invention can be pelletized despite the main component of the poorly crystalline copolyester resin having a high Tg of less than 40 ° C., and the blocking between the pellets is effective. It is prevented and can be stored for a long time in a pelletized state, and further, it can be dissolved in a general-purpose solvent, so that the industrial utility value is extremely high.

  Hereinafter, the present invention will be described in detail.

  The core-sheath type copolyester resin targeted by the present invention is a copolyester resin having a structure in which a core layer is covered with a sheath layer. The core layer is composed of a poorly crystalline copolyester having a Tg of less than 40 ° C, and the sheath layer is composed of a poorly crystalline copolyester having a Tg of 40 ° C or higher, preferably 65 ° C or higher.

  In the core-sheath copolymer polyester resin of the present invention, the mass ratio of the core layer to the sheath layer is preferably in the range of 50/50 to 99/1, more preferably 80/20 to 99/1. If the ratio of the sheath layer to the mass ratio of the core layer to the sheath layer is higher than 50/50, it is not preferable because the core component can no longer be the main component. Moreover, when the ratio of the sheath layer of the core-sheath ratio is lower than 99/1, when manufacturing industrially, it is difficult to uniformly coat the core layer with the sheath layer, which is not preferable.

  The poorly crystalline copolyester resin constituting the core layer and the sheath layer is melted at 240 ° C., extruded into a 25 ° C. water bath, 10 minutes later, taken out of the resin, and then placed in a constant temperature bath at 25 ° C. Differential scanning calorimetry is performed after standing for a day, and there is no melting point peak in both the 1st scan and the 2nd scan, or a melting point peak appears only in the 1st scan and there is no melting point peak in the 2nd scan.

  The melting point is measured at 30 ° C. as the starting temperature, heated to 250 ° C. at a rate of temperature increase of 10 ° C./min (1st scan), held for 5 minutes, and then 50 ° C./min to −50 ° C. It was cooled quickly. After holding for another 5 minutes, the temperature was raised to 250 ° C. at a rate of temperature increase of 10 ° C./min (2nd scan). The endothermic peak in the temperature rise curve obtained by the 1st scan and 2nd scan was taken as the melting point, and the endothermic peak The presence / absence was determined as an index for determining whether the polyester resin was poorly crystalline.

  The molecular weight of the copolyester resin is not particularly limited, but is usually 2000 or more, preferably 6000 or more. If the molecular weight is less than 2000, the tackiness is higher, and blocking may not be effectively prevented, which is not preferable.

  The copolymerized polyester resin is composed mainly of equimolar amounts of a dicarboxylic acid component and a glycol component, and is obtained by copolymerizing a hydroxycarboxylic acid component or the like as necessary.

  Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, aromatic dicarboxylic acids such as 4,4′-dicarboxybiphenyl, 5-sodium sulfoisophthalic acid, oxalic acid, malonic acid, and succinic acid. Saturated aliphatic dicarboxylic acids such as acid, adipic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, octadecanedioic acid, and aicosanedioic acid, fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, etc. Unsaturated aliphatic dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,5-norbornenedicarboxylic acid, alicyclic dicarboxylic acid such as tetrahydrophthalic acid, etc. Can be illustrated. These may be anhydrous.

  Examples of the glycol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1 , 3-propanediol, 2,2-diethyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1,3-propanediol, 2 -Ethyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,5-pentanediol 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decandio , 3 (4), 8 (9) -bis (hydroxymethyl) -tricyclo (5.2.1.1/2.6) decane, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol and other fats Glycol, bisphenol A, bisphenol S, bisphenol C, bisphenol Z, bisphenol AP, ethylene oxide adduct or propylene oxide adduct of 4,4'-biphenol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol , Alicyclic glycols such as 1,4-cyclohexanedimethanol, and polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

  In the copolymerized polyester resin in the present invention, a hydroxycarboxylic acid can be copolymerized depending on purposes such as appropriate flexibility, improved adhesion, and adjustment of Tg. Examples of the hydroxycarboxylic acid include p-hydroxybenzoic acid, m-hydroxybenzoic acid, o-hydroxybenzoic acid, lactic acid, oxirane, β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone. , Glycolic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxyisobutyric acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyyoshichi Examples include herbic acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid, 10-hydroxystearic acid and the like.

  If the amount is small, a tri- or higher functional carboxylic acid component or alcohol component may be added as a copolymer component. Examples of the tri- or higher functional carboxylic acid component include aromatics such as trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, and trimesic acid. Examples thereof include carboxylic acids and aliphatic carboxylic acids such as 1,2,3,4-butanetetracarboxylic acid.

  Examples of the tri- or higher functional alcohol component include glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, α-methylglucose, mannitol, and sorbitol.

  These do not necessarily need to be used alone, and can be used in combination of two or more according to the properties desired to be imparted to the resin. At this time, the proportion of the tri- or higher functional monomer is suitably about 0.2 to 5 mol% with respect to the total carboxylic acid component or the total alcohol component. If the amount added is less than 0.2 mol%, the added effect does not appear, and if the amount exceeds 5 mol% is included, gelation may exceed the gel point during polymerization.

  Moreover, monocarboxylic acid and monoalcohol may be copolymerized with the polyester resin. Examples of monocarboxylic acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexane acid, and 4-hydroxyphenyl stearic acid. Examples of the alcohol include octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, and 2-phenoxyethanol.

  The copolyester resin in the present invention can be produced by combining the above monomers and polycondensing them by a known method. For example, all the monomer components and / or low polymers thereof can be obtained under an inert atmosphere. Perform esterification by reacting at ~ 250 ° C for about 2.5 to 10 hours, and then proceed with polycondensation reaction at a temperature of 220 to 280 ° C under reduced pressure of 130 Pa or less until copolymerization is reached. Examples thereof include a method for obtaining a polyester resin.

  A polymerization catalyst can be used in the esterification reaction and polycondensation reaction.

  Suitable polymerization catalysts include titanium compounds such as tetrabutyl titanate, metal acetates such as zinc acetate and magnesium acetate, and organic tin compounds such as antimony trioxide, germanium dioxide, hydroxybutyltin oxide, and tin octylate. Can be used. The amount of the polymerization catalyst used at that time is preferably 0.5% by mass or less based on the mass of the resin produced.

  In addition, when a desired acid value or hydroxyl value is imparted to the copolymerized polyester resin, a polybasic acid component or a polyvalent glycol component is further added following the polycondensation reaction, and depolymerization is performed in an inert atmosphere. Can be done.

  The crystallinity of the copolyester resin of the present invention can be controlled by changing the combination of the acid component and alcohol component constituting the copolyester resin and the blending ratio. Generally, when the molecular structure of the acid component and alcohol component constituting the copolyester resin is expressed using a structural formula, terephthalic acid or ethylene having a chemical structural formula symmetrical to the line connecting the carboxyl group or hydroxyl group It is known that a copolymer containing a large amount of glycol, butanediol, etc. as a copolymer component has high crystallinity, but there is no clear correlation between the combination of monomers and crystallinity. Moreover, the lower the molecular weight, the higher the crystallinity of the copolyester resin.

  In the present invention, a preferred acid component as a poorly crystalline copolyester resin, a combination of alcohol components, terephthalic acid as the acid component, ethylene glycol and 1,4-butanediol as the alcohol component, asymmetric isophthalic acid, Those in which neopentyl glycol, 1,2-propanediol and the like are copolymerized are preferred. As a blending ratio, it is preferable to blend 25% or more of terephthalic acid with respect to the entire acid component and 25% or more of ethylene glycol or 1,4-butanediol with respect to the entire alcohol component. Any combination can be selected while maintaining the balance.

  The copolymer polyester resin of the present invention has a solubility (25 ° C.) in a solvent of at least one selected from the group consisting of cyclohexanone, 2-butanone, toluene, and ethyl acetate at 25 ° C. of 10% by mass or more. There is a need. When the solubility is not more than 10% by mass, workability when used as a paint or a coating agent is lowered, which is not preferable. There is no particular upper limit on solubility, but 50% by mass or less is preferable so that the viscosity of the solution does not become too high.

  The copolymer polyester resin used for the core layer and the sheath layer has a solubility (25 ° C.) of 10 or more in one or more solvents selected from the group consisting of cyclohexanone, 2-butanone, toluene, and ethyl acetate at 25 ° C., respectively. It must dissolve at mass% or higher. When the solubility is not 10% by mass or more, the core-sheath copolymer polyester resin pellet composed of the core layer and the sheath layer is difficult to dissolve in a general-purpose solvent, which is not preferable.

  The total light transmittance of a solution obtained by dissolving the copolymerized polyester resin of the present invention at 10% by mass in one or more solvents selected from the group consisting of cyclohexanone, 2-butanone, toluene, and ethyl acetate is 80% or more. is necessary. If the total light transmittance is lower than 80%, the usage is greatly limited when used as a paint or a coating agent.

Further, the total light of a solution obtained by dissolving the copolymer polyester resin used for the core layer and the sheath layer in 10% by mass or more in one or more solvents selected from the group consisting of cyclohexanone, 2-butanone, toluene, and ethyl acetate, respectively. The transmittance needs to be 80% or more. When the total light transmittance of the copolymer polyester resin used for the core layer and the sheath layer is lower than 80%, the total light transmittance of the solution of the core-sheath type copolymer polyester resin pellet composed of the core layer and the sheath layer is Since it becomes lower than 80%, it is not preferable.

  In addition, the core layer and the copolymer polyester used for the core layer include, if necessary, one or more solvents selected from the group consisting of cyclohexanone, 2-butanone, toluene, and ethyl acetate as a core-sheath type copolymer polyester resin. The total light transmittance of the solution dissolved in 10% by mass in the range of 80% or more is an ultraviolet ray preventing agent, a light stabilizer, an antifogging agent, an antifogging agent, an antistatic agent, a flame retardant, a coloring preventing agent, and an antioxidant. You may add additives, such as an agent, a filler, and a pigment. The total light transmittance of the dissolved solution is greatly influenced by the type, color tone, and particle size of the additive.For example, even when an additive having the same particle size is used, the black additive is better when the white additive is used. There is a tendency for the total light transmittance to be higher than that used, and even when the same type of additive is used and the same addition amount, the case where the particle diameter is 10 μm or less and the case where the particle diameter is 100 nm are used. In this case, the total light transmittance tends to be higher when a particle having a smaller particle diameter is used. The amount of additive for making the total light transmittance 80% or more depends on the core-sheath ratio, the kind of additive, and the amount of the additive. For example, the mass ratio of the core layer to the sheath layer is 80/20. When the agent is talc, adding 0.5% or more of talc with respect to the mass of the copolyester of the sheath layer is not preferable because the total light transmittance is lower than 80%.

  The solubility differs depending on the type of additive and the amount of the additive, but when an additive that has been hydrophobized so as to dissolve in an organic solvent is used, the solubility is relatively increased.

  Next, the manufacturing method of the core-sheath-type copolymer polyester resin pellet of this invention is demonstrated.

  The production method of the present invention comprises substantially (1) a step of separately melting the copolyester resin of the core layer and the sheath layer, and (2) extruding the melted copolyester resin into a strand having a core-sheath structure and cooling. Thereafter, it is divided into a step of pelletizing and (3) a step of drying the pellet.

  First, the step (1) of separately melting the copolyester resins of the core layer and the sheath layer will be described. In the present invention, the copolyester resin of the core layer and the sheath layer can be melted by an arbitrary method. For example, the copolymer polyester used for a core layer and a sheath layer is melted at a temperature 30 ° C. or more higher than the glass transition point using a known melting kettle, and each is extruded with an extruder equipped with a gear pump. Also, the sheath layer copolymer polyester is melted using a known melting kettle and extruded with an extruder equipped with a gear pump, while the core layer copolymer polyester is polymerized with a known polymer kettle and extruded while metering with a gear pump. A method is mentioned.

  Next, the process of extruding the melted copolyester resin (2) onto a strand having a core-sheath structure, cooling, and pelletizing will be described.

  In the present invention, the copolyester resin separately melted can be made into a strand having a core-sheath structure using a core-sheath nozzle. As the core-sheath nozzle, a known core-sheath nozzle can be used. For example, when copolyester resins melted separately are made into strands using the nozzles described in Japanese Patent Nos. 3872169 and 3834132, the core layer and the sheath layer of the copolyester are formed for each strand. Distributed and core-sheathed strands can be obtained.

  The core-sheath strand can be cooled in a cooling bath and then pelletized with a known open bath type strand cutter, underwater type strand cutter, air-cooled side-cut pelletizer, or the like. Examples of the open bath type strand cutter include SCC series manufactured by Nippon Steel Works, Ltd., and examples of the underwater type strand cutter include APS series manufactured by Tokuki Co., Ltd. Company fan plastic fan cutter.

  The discharge speed and discharge amount of the resin are not particularly limited as long as the cooling speed and the discharge amount are balanced.

  Although the temperature of a cooling bath will not be specifically limited if a polymer can be cooled, 150 degrees C or less is preferable, 60 degrees C or less is more preferable, 20 degrees C or less is further more preferable. When the temperature of the cooling bath is higher than 150 ° C., the cooling effect is lowered, which is not preferable. The cooling time is not particularly limited as long as the polymer can be cooled, but is preferably 20 minutes or less. If the cooling time is longer than 20 minutes, it is economically disadvantageous.

In the present invention, it is necessary to dilute and use an aqueous dispersion in which copolyester resin fine particles having an antiblocking effect are dispersed in a cooling bath . By adding the aqueous dispersion of the copolymer polyester resin to the cooling tank, the aqueous dispersion adheres to the pellet surface after cooling, and after drying, the fine particles of the copolymer polyester resin can adhere to the pellet surface. It is possible to suppress the stickiness.

  The average particle diameter of the copolyester resin fine particles dispersed in the copolyester resin aqueous dispersion needs to be 500 nm or less, preferably 200 nm or less. The type of copolymer polyester resin is not particularly limited as long as it is dispersed in water and does not have adhesiveness. If the average particle diameter is larger than 500 nm, it is not preferable because the dispersibility is not good and the particles are not uniformly dispersed.

The glass transition point of the copolyester resin fine particles dispersed in the copolyester resin aqueous dispersion must be 40 ° C. or higher, preferably a poorly crystalline resin or crystal having a Tg of 60 ° C. or higher. Resin is preferred. Examples thereof include KA-3556 and KA-5034 manufactured by Unitika. It is not always necessary to use one type of copolymerized polyester resin aqueous dispersion, and a mixture of two or more types can be used.

The addition amount of the copolymerized polyester resin aqueous dispersion should be such that the resin solid content of the aqueous dispersion is 0.1 to 5% by mass with respect to the circulating water used for cooling the resin , preferably It is preferable to add 0.5 to 3% by mass, optimally 0.5 to 2% by mass. When the resin solid content of the aqueous dispersion is less than 0.1% by mass with respect to the circulating water, the blocking resistance is not sufficiently exhibited, and when it is added more than 5% by mass, the resin melts during pellet drying. Since it becomes easy to wear, it is not preferable.

  Next, (3) the step of drying the pellet will be described.

  In the present invention, the method is not particularly limited as long as the pellets can be dried. For example, vacuum drying, hot air drying, natural drying or drying with cold air can be used.

EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited only to an Example. In addition, the raw material used in the Example and the evaluation method of a physical property are as follows.
(1) Composition of core-sheath copolymer polyester
^{It was determined by 1} H-NMR analysis (manufactured by Varian, 300 MHz, solvent chloroform-d, measurement temperature 25 ° C.).
(2) Number-average molecular weight of core-sheath copolymer polyester The number-average molecular weight is determined using GPC analysis (liquid feeding unit LC-10ADvp type and UV-visible spectrophotometer SPD-6AV type manufactured by Shimadzu Corporation), detection wavelength: 254 nm, solvent: tetrahydrofuran, polystyrene conversion).
(3) Core-sheath type copolyester, glass transition point of copolyester of core-sheath layer and sheath-layer respectively. Using 10 mg of resin as a sample, using a DSC (Differential Scanning Calorimetry) apparatus (DSC7 type manufactured by PerkinElmer), The starting temperature was 30 ° C., the temperature was raised to 250 ° C. at a heating rate of 10 ° C./min (1st scan), held for 5 minutes, and then rapidly cooled to −50 ° C. at 50 ° C./min. After holding for another 5 minutes, the temperature was raised to 250 ° C. at a rate of temperature increase of 10 ° C./min (2nd scan), and the intersection of two bending point temperatures derived from the glass transition in the temperature rise curve obtained by 2nd scan Was the glass transition point, and the endothermic peak in the temperature rise curve obtained by 2nd scan was taken as the melting point.
(4) Evaluation of blocking resistance of core-sheath type copolyester 100 g of resin is subjected to a load of 25 kg per 800 cm ^{2 and} left in a constant temperature bath at 40 ° C. for 3 days, and then the pellets are not fused at all. (Circle), it evaluated as (circle) if there were more than 10 g and what was evaluated as (circle), and what was evaluated as pass if the thing which the pellets fuse | melted is 10 g or less.
(5) Solubility Evaluation of Core-Sheath Copolyester Into a glass container, 10 g of resin and 90 g of 2-butanone / toluene mixed solvent (mass ratio 1/1) are added (concentration 10 mass%), and a paint shaker is used. The solution was vibrated at 25 ° C. for 6 hours, and the dissolved state was observed. Those that were dissolved were designated as “◯”, and those that did not dissolve were designated as “x”. The same evaluation was performed on the resin 30 g and the mixed solvent 70 g (concentration 30% by mass).
(6) Total light transmittance of core-sheath copolymer polyester solution 10 g of resin and 90 g of 2-butanone / toluene mixed solvent (mass ratio 1/1) are placed in a glass container (concentration 10 mass%), and a paint shaker is used. The sample was vibrated at 25 ° C. for 6 hours, and immediately after melting, an appropriate amount of sample was placed in a quartz glass cell and measured using a HazeMeter NDH2000 manufactured by Nippon Denshoku Industries.

(Manufacture of copolyester resin)
Production Example 1
831 g (50 mol parts) of terephthalic acid, 831 g (50 mol parts) of isophthalic acid, 604 g (58 mol parts) of neopentyl glycol, 540 g (87 mol parts) of ethylene glycol, and 500 g (5 mol parts) of polytetramethylene glycol 1000 While stirring, the mixture was heated in an autoclave at 240 ° C. for 3 hours for esterification reaction. Next, while maintaining 240 ° C., 2.0 g of tetrabutyl titanate was added as a catalyst, the pressure of the system was gradually reduced to 13 Pa after 1.5 hours, and a polycondensation reaction was performed. After 4 hours, the resulting product was designated as polyester A, and its final composition and properties are shown in Table 1.
Production Examples 2-5
The monomer used and the charged mole part were changed, and the same operation as in Production Example 1 was performed to obtain Copolyester Resin B to Copolyester Resin E in Production Examples 2 to 5. Table 1 shows the final compositions and characteristics of the obtained copolyester resins B to E.

( Reference Example 1 )
Polyester A is polymerized as a core component so that the core component: sheath component is 90:10 (mass ratio), then weighed with a gear pump, and at the same time, prepolymerized polyester B is melted with an extruder as a sheath component. The core-sheath strand was extruded into a 10 ° C. cooling bath. The strand was cooled in a cooling bath for 1 minute and then pelletized with a star plastic fan cutter to obtain a core-sheath copolymer polyester pellet.
( Reference Examples 2-3 , Comparative Examples 1, 2)
Pellets were produced in the same manner as in Reference Example 1 except that the resin of the core component, the resin of the sheath component, and the mass ratio of the core component and the sheath component were changed as shown in Table 2.
( Example 1 )
Cooling water in which the resin of the core component and the resin of the sheath component are changed as shown in Table 2, and an aqueous copolymerized polyester dispersion (KA-3556 manufactured by Unitika, Tg = 80 ° C.) is added to a solid content of 3% by mass. Pellets were produced in the same manner as in Reference Example 1 except that was used.
( Examples 2 and 3 )
The aqueous copolyester dispersion of Example 1 was changed to KA-5034 (Tg = 67 ° C.) manufactured by Unitika or KA-1449 (Tg = 41 ° C.) manufactured by Unitika, and the cooling water added with the solid content shown in Table 2 Except that was used, pellets were produced in the same manner as in Example 1 .
(Comparative Examples 3 and 4)
In Comparative Example 3, instead of Polyester B, Polyester B containing 40% by mass of carbon black (RCF # 44 manufactured by Mitsubishi Carbon Black) was used as the sheath component. In Comparative Example 4, silica (Silo Hovic 702 manufactured by Fuji Silysia) was used. A pellet was produced in the same manner as in Example 1 except that polyester B containing 40% by mass of a hydrophobized product obtained by chemically reacting an organosilicon compound on the surface of Sicilia 430 manufactured by Fuji Silysia was used.

The results of blocking resistance evaluation and solubility evaluation of the pellets obtained in Examples 1 to 3, Reference Examples 1 to 3, and Comparative Examples 1 to 4 are shown together in Table 2.

The pellets obtained in Examples 1 to 3 were all pellets of poorly crystalline copolyester resin that had good evaluation of anti-blocking evaluation and solubility evaluation and could be stored for a long period of time. On the other hand, since the comparative example 1 used copolymer polyester with Tg of 40 degreeC for a sheath component, it was a thing with bad blocking resistance. Moreover, since the ratio of the core component and the sheath component was high in Comparative Example 2, the core layer was no longer the main component. Moreover, since the comparative example 3 added the additive to the sheath component, the solubility evaluation of the pellet was bad. Further, in Comparative Example 4, since the additive was added to the sheath component, the additive was dispersed, but the solubility evaluation was poor, and the total light transmittance of the solution in which the pellet was dissolved was poor.

Thus, by coating a copolymer polyester having a Tg of 40 ° C. or more, for the first time, a pellet containing a copolymer polyester having a Tg of 40 ° C. as a main component can be obtained, and can be dissolved in a general-purpose solvent. A pellet of poorly crystalline copolyester resin having a long-term storage property with a total light transmittance of 80% or more was obtained.

Claims (1)

  A core-sheath type strand having a poor crystalline copolyester resin having a glass transition point of less than 40 ° C. as a core layer and a poor crystalline copolyester resin having a glass transition point of 40 ° C. or more as a sheath layer is melt extruded and cooled. Using circulating water added so that the resin solid content of the aqueous dispersion of the polyester resin having a glass transition point of 40 ° C. or higher is 0.1 to 5% by mass as a medium, cooling the strand, and then cutting into pellets A process for producing a core-sheath copolymer polyester resin pellet characterized by