JP3750592B2 - Method for producing crystalline polymer pellets that are difficult to block - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing crystalline polymer pellets used for molding materials, adhesives, paints, coating agents, etc., for example, copolyester pellets, and in particular, a crystalline polyester having a crystallinity of a specific value or more. The present invention relates to a method for producing a copolyester pellet having high crystallinity by suppressing the occurrence of blocking by handling an uncrystallized pellet in the presence of.
[0002]
[Prior art]
Conventionally, crystalline thermoplastic polyesters, such as low melting point and low glass transition point, such as aromatic or aliphatic copolyesters, are used for molding materials, adhesives, paints, coating agents, etc. . Such a copolyester resin is obtained by extruding the melt after the polycondensation reaction in the polycondensation reactor into strands or sheets, cooling and solidifying with water, and cutting into pellets using a pelletizer. Is done. Since the pellets immediately after cutting contain moisture, when the undried pellets are heated and melted in an apparatus such as an extruder or applicator in applications such as molding materials and adhesives, residual moisture Degradation of quality such as hydrolysis due to water, and troubles due to bubbles formed by evaporation of moisture occur. Therefore, a heat drying process is necessary for removing moisture from the pellets.
[0003]
However, during the pellet drying process, if the pellets are not sufficiently crystallized, there arises a problem that the pellets are blocked. Therefore, it is usual to pass through a crystallization step for heating the pellets to increase the crystallinity before drying. However, resins with a low melting point and glass transition point that are prone to blocking not only cause blocking when pellets cut by a pelletizer are transferred to the crystallization process, but also increase the amount of resin input to increase productivity. If this is done (the resin concentration in the process is increased), there is a problem that blocking occurs even during the crystallization process.
[0004]
Japanese Patent Application Laid-Open No. 5-131440 proposes a manufacturing method in which a resin cut into pellets is heated in warm water to increase the degree of crystallinity. Depending on the resin concentration, blocking tends to occur even during the crystallization process as described above, and this is not a fundamental solution.
Japanese Patent Application Laid-Open No. 7-2232221 and Japanese Patent Application Laid-Open No. 8-155952 propose a method of cutting a cooled solidified strand or sheet while stretching. However, this method has a problem that the resin breaks during stretching when the resin does not have sufficient elasticity.
[0005]
On the other hand, in order to prevent blocking, a method of adhering paraffin or silicone to the pellet surface prior to heat drying shown in JP-A-50-158629, amorphous silica shown in JP-B-62-19463 A method of dry blending and then drying treatment, an ester with an alkali metal salt of a higher fatty acid having 8 to 22 carbon atoms or a sorbitol condensate as disclosed in JP-A-60-23449, a polycarboxylic acid type polymer A method of adhering an alkali metal salt of an electrolyte and an oxy-ether-oxy-propylene block polymer surfactant to the pellet surface has been proposed. However, it is desired that these anti-adhesive agents are not used as much as possible because they adversely affect the physical properties of the resin.
[0006]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems in the production of crystalline polymers such as conventional copolyesters, and efficiently crystallizes crystalline polymers without blocking the pellets during transfer and heat treatment. It is an object of the present invention to provide a method for producing a crystalline polymer that is difficult to block, particularly a copolyester, by increasing the degree.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the problems of the conventional methods as described above, the present inventors have conducted a pellet transfer step to the crystallization step or a heating treatment in warm water to obtain a degree of crystallinity. In the process of increasing the pH, the presence of a resin whose crystallinity has been increased to a certain value or more can prevent the pellets from blocking each other, increase the crystallization without problems, and prevent the subsequent blocking, thereby increasing the productivity. The present inventors have found out that it can be increased and have completed the present invention.
[0008]
That is, the present invention includes a step of extruding a melt of a crystalline polymer into a strand or a sheet, cooling and solidifying, and then transferring a pellet after cutting with a pelletizer to a crystallization apparatus and / or a step of increasing the degree of crystallization by heat treatment. In the present invention relates to a method for producing a crystalline polymer, characterized in that pellets in an uncrystallized state are handled in the presence of the crystalline polymer whose crystallinity is separately adjusted to 5% or more. . Hereinafter, the present invention will be described in more detail.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Crystalline polymer The crystalline polymer that is the subject of the present invention is a crystalline thermoplastic resin, specifically, a polyester resin, a polyamide resin, a polyolefin resin, a polyacetal resin, or the like. The crystalline polymer preferably used in the present invention is a copolyester resin, and particularly preferably a crystalline polyester resin having a melting point of 150 ° C. or lower and a glass transition point of 20 ° C. or lower.
[0010]
Although it does not limit as a repeating unit (monomer) which comprises the polyester resin which can be used by this invention, the following components can be mention | raise | lifted.
Examples of the acid component include aromatics such as terephthalic acid, isophthalic acid, phthalic anhydride, α-naphthalenedicarboxylic acid, β-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, and ester formers thereof. Aliphatic dicarboxylic acids such as dicarboxylic acid, oxalic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecylenic acid, dodecanedioic acid and their ester formers, 1,4-cyclohexanedicarboxylic acid, tetrahydroanhydride Examples thereof include alicyclic dicarboxylic acids such as phthalic acid, hexahydrophthalic anhydride and esters thereof. Also, polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid can be used in combination as long as gelation does not occur during polyester synthesis.
[0011]
Examples of the polyol component include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, Fats such as 1,8-octanediol, 1,9-nonanediol, neopentyl glycol, 3-methylpentanediol, 2,2,3-trimethylpentanediol, diethylene glycol, triethylene glycol, dipropylene glycol Alicyclic glycols such as aliphatic glycols, 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol, and aromatic glycols such as bisphenol A. Polyhydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol can also be used in combination as long as gelation does not occur during polyester synthesis.
[0012]
In the crystalline polymer pellets produced in the present invention, a polymer containing a modifier other than the crystalline polymer can also be used. For example, when the crystalline polymer is a copolyester, a crystalline polyester obtained by blending this polyester with a modifier other than polyester can also be used. That is, as a modifier, polyethylene resin, polypropylene resin, styrene resin, polyurethane resin, epoxy and modified epoxy resin, phenol resin, phenoxy resin, petroleum resin, rosin and modified rosin resin, organic alkoxylane, calcium carbonate, zinc oxide, oxidation Inorganic fillers such as titanium, talc, clay, bentonite, fumed silica, silica powder, antioxidants such as hindered phenols, coloring pigments, anti-sagging agents, surface conditioners, ultraviolet absorbers, light stabilizers and other resins Stabilizers can be blended as needed.
[0013]
The crystalline copolyester resin that can be used in the present invention is produced by an ordinary melt polymerization method in which raw materials and a catalyst are charged and heated at a temperature equal to or higher than the melting point of the product. The obtained molten resin is extruded into a strand or a sheet through a die or the like, and the resin is cooled and solidified by a method such as passing through a water tank or spraying water. Next, the cooled or solidified strand or sheet is cut into pellets by a pelletizer in the presence of water or warm water. In particular, in a resin having a low melting point or glass transition point, the pellet after cutting is likely to be blocked, and thus a step of increasing the crystallinity by a heating treatment using hot water or the like is required.
[0014]
The pellets are transferred from the pelletizer to a crystallization apparatus for increasing the degree of crystallinity using a pump such as a slurry pump, and then in a crystallization apparatus equipped with a stirrer, a temperature suitable for crystallization (usually 20 to 50 ° C. ), The crystallinity is increased until the pellets do not block each other. The pellets whose crystallinity is increased and no longer block are dried after dehydration using a dehydrator such as a centrifugal dehydrator.
[0015]
The present invention uses only water or hot water to prevent the pellets from blocking in the step of transferring the pellets cut by the pelletizer to the crystallization apparatus and / or the step of increasing the crystallization degree by heat treatment. In addition, polymer pellets having the same composition as the non-crystalline polymer whose crystallinity was separately increased to 5% or more were mixed at a ratio of 5 to 50% by mass with respect to the total amount of the non-crystalline polymer. This is a method for producing a crystalline polymer that can prevent blocking during transportation or when increasing the degree of crystallinity. If the concentration of the pellet having a crystallinity of 5% or more is less than 5% by mass, a sufficient effect cannot be obtained. On the other hand, even if the concentration of the pellets exceeds 50% by mass, the effect of preventing blocking is obtained, but the processing amount is lowered and the productivity is deteriorated.
[0016]
The crystallinity referred to in the present invention indicates the state of crystallization of the crystalline polymer, and can be determined from the crystallization energy, which is the endothermic amount at the crystallization temperature of DSC (differential scanning calorimeter). That is, the measured value of the crystallization energy of the pellet mixed and used in the pellet handling process is crystallized for 10 days or more at the fastest crystallization temperature in the range of the resin melting point-30 ° C to the resin melting point-80 ° C. It is a value obtained by multiplying 100 by the value divided by the crystallization energy of the pellets.
In the present invention, the crystallinity of the crystalline polymer mixed with the non-crystalline polymer pellets to increase the crystallinity is 5% or more, preferably 10% or more.
When pellets having a crystallinity of less than 5% are used, the anti-blocking effect is not sufficient.
[0017]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by this.
[Example 1]
The main raw materials are dimethyl terephthalate, adipic acid, sebacic acid, ethylene glycol, and 1,4-butanediol. After transesterification and esterification reaction at 170 to 250 ° C under normal pressure, at 230 to 250 ° C under reduced pressure. Excess glycol is removed by a melt polycondensation reaction to obtain a copolyester of 80 g / 10 min with a melt index (value measured according to JIS-K-6760-1977 in g / 10 min). It was. The composition of this copolyester was determined by H ¹ -NMR analysis in which the acid side was terephthalic acid / adipic acid / sebacic acid = 64/18/18 (molar ratio) and the glycol side was ethylene glycol / 1,4-butanediol = 55 / 45 (molar ratio). Further, the melting point by a microscopic formula was 110 ° C., and the glass transition point by DSC was −0.5 ° C.
[0018]
This melted copolyester resin was extruded in a strand form from the reactor, cooled in a 20-25 ° C. water bath, then cut into cylindrical pellets having a diameter of 3 mm and a length of 4 mm with a pelletizer, and a solids transportation pump However, there was a frequent problem that pellets were blocked inside the pump casing, the feed pipe, and the crystallization tank.
Therefore, pellets whose crystallinity is increased to 15 to 20% in the crystallization tank (pellets taken out from the crystallization tank and dried after dehydration, and the pellets are subjected to a pressure of 0.2 kg / cm ² at a normal temperature of 10 When the pellets were not blocked even when added for a minute) on the suction side of the solid material transport pump at a ratio of 10%, the blocking phenomenon did not occur.
[0019]
[Example 2]
Mainly using dimethyl terephthalate, sebacic acid, 1,4-butanediol, 1,6-hexanediol, and after performing transesterification and esterification at 150 to 210 ° C. under normal pressure, 210 to 250 ° C. under reduced pressure. The excess glycol is removed by a melt polycondensation reaction to obtain a copolyester having a melt index (value measured according to JIS-K-6760-1977 in g / 10 minutes) of 300 g / 10 minutes. It was. According to the constitution of this copolymer polyester, the acid side is terephthalic acid / sebacic acid = 60/40 (molar ratio) by H ¹ -NMR analysis, and the glycol side is 1,4-butanediol / 1,6-hexanediol = 40/60. (Molar ratio). Further, the melting point by a microscopic formula was 69 ° C., and the glass transition point by DSC was −31 ° C.
[0020]
This melted copolyester resin was extruded in a strand form from the reactor, cooled in a 10-15 ° C. water bath, then cut into cylindrical pellets having a diameter of 3 mm × length of 4 mm with a pelletizer, and a solids transportation pump However, there was a frequent problem that pellets were blocked inside the pump casing, the feed pipe, and the crystallization tank.
Therefore, pellets whose crystallinity is increased to 25 to 30% in the crystallization tank (pellets taken out from the crystallization tank and dried after dehydration, and the pellets are subjected to a pressure of 0.2 kg / cm ² at a normal temperature of 10 When the above-mentioned transfer was carried out after mixing the pellets that do not block even if added for a minute) at a ratio of 20% by mass on the suction side of the pump for transporting solid matter, the blocking phenomenon did not occur.
[0021]
【The invention's effect】
By using the method for producing a crystalline polymer pellet according to the present invention, the crystalline polymer without causing troubles due to blocking between pellets in a transfer equipment or a crystallization tank in a pump or piping after the pellet cutting step. In particular, it can be widely used in the chemical industry for producing crystalline polymers such as polyester.

Claims (3)

In the process of extruding the crystalline polymer melt into strands or sheets, cooling and solidifying it , transferring the pellets after cutting with a pelletizer to a crystallizer, and / or increasing the crystallinity by heat treatment , separate crystallization A method for producing a crystalline polymer pellet, comprising mixing the crystalline polymer pellets whose degree has been adjusted to 5% or more and handling pellets in an uncrystallized state.  The method for producing a pellet of crystalline polymer according to claim 1, wherein the pellet in an uncrystallized state is handled in a state where 5 to 50% by mass of a crystalline polymer pellet having a crystallinity of 5% or more is mixed. 3. The method for producing a crystalline polymer pellet according to claim 1, wherein the crystalline polymer is a copolyester.