JP2000271928A - Manufacture of heat resistant thermoplastic resin pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide heat resistant thermoplastic resin pellets having favorable quality characteristics without developing coloration, thermal deterioration, crack or the like. SOLUTION: This manufacturing method includes a process for extruding a heat resistant thermoplastic resin 20 under molten state through fine holes 14 provided in an extrusion die 12, a process for cutting a maleimide-based copolymer under molten state just after the extrusion through the fine holes 14 and a process for obtaining a maleimide-based copolymer pellets 24 under solidified state through the cooling of the cut maleimide-based copolymer 24 under molten state. The heat resistant thermoplastic resin 20 can have a glass transition temperature of 150-300 deg.C and can be a resin including a maleimide- based copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a heat-resistant thermoplastic resin pellet, and more particularly, to a method for producing a heat-resistant thermoplastic resin comprising a maleimide-based copolymer or the like and having a pellet form which is easy to handle. And a heat-resistant thermoplastic resin pellet obtained by such a method.

[0002]

2. Description of the Related Art A maleimide copolymer is known to be a thermoplastic resin having a high heat deformation temperature and a high thermal decomposition temperature. Generally, the heat resistance and the heat resistance of products using other thermoplastic resins are known. It is used to improve impact properties and moldability.

[0003] A maleimide-based copolymer is usually produced by copolymerizing a maleimide-based monomer with another monomer copolymerizable therewith. As the polymerization method, various polymerization methods such as emulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization are employed.

After completion of the polymerization, the reaction mixture is supplied directly or after heating and drying to a vent type extruder to remove volatile components, extrude a polymer in a molten state into a strand, and the strand is subjected to a predetermined process. A method of cutting into pellets at intervals is known (JP-A-59-126411, 59-58006,
57-135814, 50-40688, 57-496
03, 50-40687, 63-147501 and JP-A-3-49925). Such a method is also used as a method for obtaining a maleimide-based copolymer (JP-A-2-51514, JP-A-63-8).
No. 9806). Pellets are advantageous in that they do not contain air and are not bulky as compared to powders and the like, and are excellent in handleability, weighability, and the like.

[0005] The applicant of the present invention disclosed in Japanese Patent Application Laid-Open No. 6-126739 discloses that a strand of a maleimide-based copolymer melt-extruded by an extruder is cooled to 180 to 250 ° C and then cut. To produce pellets by cooling to room temperature. This method has an advantage that the maleimide-based copolymer is not exposed to a high temperature for a long time, so that problems of coloring and thermal deterioration hardly occur.

[0006]

However, in the method of cutting the maleimide copolymer strand described above, it is difficult to properly perform temperature control, and environmental conditions such as temperature and humidity of the installation environment of the apparatus are different. Then, the cooling rate of the maleimide-based copolymer changes, and the tension of the strand changes. For this reason, there has been a problem that characteristics such as the quality and shape of the maleimide-based copolymer vary greatly.

If a melt-extruded maleimide-based copolymer is formed into a strand and cooled to a certain extent before cutting, a considerable time elapses before cutting, and during that time the molten maleimide-based copolymer is melted. It is believed that the coalescence is susceptible to external environmental conditions. It is considered that the contact of the surface of the maleimide-based copolymer in the molten state with air for a long time also has an effect. For this reason, it takes time and effort to adjust and manage working conditions such as the temperature of the maleimide-based copolymer one by one in accordance with changes in external environmental conditions, which has been a factor in reducing production efficiency.

Further, residual stress and strain are generated in the maleimide copolymer due to the load when the solid strand is cut, and cracks and cracks are generated in the obtained pellets.
There is also a problem that the quality characteristics of the pellets are degraded due to chipping of some of the pellets. The cut pellets have sharp corners in the cut surface. These sharp corners are easily shaved during the handling of the pellets to generate fine powder, and the quality of the pellets deteriorates due to the fine powder during transport handling and use of the pellets.

A maleimide-based copolymer having excellent heat resistance has a higher glass transition temperature than a general thermoplastic resin and has a relatively brittle property. It is considered that cracking and generation of fine powder easily occur.

The problems with the maleimide-based copolymer described above are not limited to the maleimide-based copolymer, but may also be the same with various heat-resistant thermoplastic resins.

An object of the present invention is to provide a heat-resistant thermoplastic resin pellet made of a heat-resistant thermoplastic resin such as a maleimide-based copolymer and having good quality characteristics without causing coloring, thermal deterioration, cracks and the like. That is.

[0012]

The method for producing heat-resistant thermoplastic resin pellets according to the present invention is a method for producing heat-resistant thermoplastic resin pellets by melt extrusion using an extruder having an extrusion die. Step.

A step of extruding a heat-resistant thermoplastic resin in a molten state from pores provided in the extrusion die.

A step of cutting the heat-resistant thermoplastic resin in a molten state immediately after being extruded from the pores.

A step of cooling the cut heat-resistant thermoplastic resin in a molten state to obtain solidified heat-resistant thermoplastic resin pellets. [Heat-Resistant Thermoplastic Resin] Various heat-resistant thermoplastic resins such as the maleimide-based copolymer described above are used.

The maleimide-based copolymer is produced, for example, by copolymerizing a maleimide-based monomer (a) and another monomer (b) copolymerizable therewith.

The polymerization method includes emulsion polymerization, suspension polymerization,
Various polymerization methods such as solution polymerization and bulk polymerization can be adopted,
Among these, solution polymerization and bulk polymerization are preferred. In emulsion polymerization, the glass transition temperature (T
g) is high, so that salting-out operation is difficult, or impurities such as an emulsifier are mixed, resulting in low impact resistance and easy coloring. In addition, in the case of suspension polymerization, for example, when a maleimide-based monomer is copolymerized with an aromatic vinyl-based monomer, an alternating copolymer of these monomers is easily produced or the produced copolymer is produced. May have a high Tg, so that the polymerization rate may easily decrease. This is because the above does not occur in the case of solution polymerization or bulk polymerization.

The maleimide monomer (a) is represented by the following formula (1):

[0019]

Embedded image

[In the formula (1), R ¹ is hydrogen or an alkyl group, a cycloalkyl group, a substituted alkyl group, an aryl group or a substituted aryl group having 1 to 15 carbon atoms. For example, maleimide, N-methylmaleimide, N-ethylmaleimide, N
-Propylmaleimide, N-isopropylmaleimide,
N-butylmaleimide, N-isobutylmaleimide, N
Tert-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-chlorophenylmaleimide, N-methylphenylmaleimide, N-bromophenylmaleimide, N-naphthylmaleimide, N
-Laurylmaleimide, 2-hydroxyethylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide, N-benzylmaleimide and the like. Species or two or more can be used. In particular, it is preferable to use one or both of phenylmaleimide and cyclohexylmaleimide since a copolymer which is easily available and has excellent heat resistance can be obtained.

As the other monomer (b), a compound having an ethylenically unsaturated bond is used, for example, for the purpose of improving impact resistance, solvent resistance, and compatibility. Specifically, aromatic vinyl monomers such as styrene and α-methylstyrene; unsaturated nitriles such as acrylonitrile, methacrylonitrile and phenylacrylonitrile; and having 1 to 18 carbon atoms including a cycloalkyl group and a benzyl group. (Meth) acrylates having an alkyl group of [for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate,
Tertiary butyl (meth) acrylate, amyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acryl Benzyl acid, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, etc.]; olefins such as ethylene, propylene, isobutylene, diisobutylene; dienes such as butadiene and isoprene; Vinyl halides such as vinyl chloride, vinylidene chloride and vinyl bromide; vinyl ethers such as methyl vinyl ether and butyl vinyl ether; vinyl esters of saturated monocarboxylic acids such as vinyl acetate and vinyl propionate; allyl acetate and propion Allyl esters or methallyl esters of saturated aliphatic monocarboxylic acids such as allyl; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, diallyl phthalate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) ) Acrylate, dipentaerythritol hexa (meth) acrylate, dimethacrylate of bisphenol A ethylene oxide or propylene oxide adduct, di (meth) acrylate of halogenated bisphenol A ethylene oxide or propylene oxide adduct, tri (isocyanurate) Di- or tri (meth) acryle of ethylene oxide or propylene oxide adduct of (meth) acrylate, isocyanurate Multivalent such bets (meth) acrylate; polyhydric arylate such as triallyl isocyanurate; glycidyl (meth) acrylate, allyl glycidyl ether, (meth) acrylic acid,
Examples thereof include itaconic acid, maleic acid, fumaric acid and half-esterified products thereof.
Although more than one kind is used, the kind and the use amount may be selected without departing from the object of the present invention.

Among the above, preferred monomers as the monomer (b) are aromatic vinyl monomers, nitriles and (meth) acrylic esters, especially styrene, α
-Methylstyrene, acrylonitrile, methyl methacrylate are preferred.

The following are specifically listed as the above-mentioned aromatic vinyl monomers.

The aromatic vinyl monomer is represented by the following formula (2):

[0025]

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[In the formula (2), R ² , R ³ and R ⁴ are
Each is independently hydrogen or an alkyl group having 1 to 5 carbon atoms, and R ⁵ is an aryl group or a substituted aryl group. ]
For example, styrene; o-methylstyrene, m-methylstyrene, p-methylstyrene (o-, m-, p-methylstyrene is also referred to as vinyltoluene), 1,3-dimethylstyrene Alkylstyrenes such as, 2,4-dimethylstyrene, ethylstyrene and p-tert-butylstyrene; α-methylstyrene, α
-Ethylstyrene, α-methyl-p-methylstyrene;
Vinylnaphthalene; halogenated styrenes such as o-chlorostyrene, m-chlorostyrene, p-chlorostyrene and 2,4-dibromostyrene; halogenated alkylstyrenes such as 2-methyl-4-chlorostyrene; divinylbenzene and the like. And one or more of these can be used. From the viewpoint of the balance between productivity and physical properties, it is particularly desirable to use at least one selected from the group consisting of styrene, vinyltoluene and α-methylstyrene. When an aliphatic vinyl monomer is used without using an aromatic vinyl monomer, the reactivity of the monomer is low, the heat resistance of the obtained copolymer is low, and the hygroscopicity is low. Although it may be large, it is advantageous in terms of transparency and heat resistance, and is appropriately selected depending on the purpose of use.

The maleimide-based monomer (a) is a component for improving the heat resistance of the obtained copolymer. The amount of the maleimide-based monomer (a) and the other monomer (b) Can be changed depending on the type and the ratio.

The proportion of the maleimide-based monomer unit contained in the maleimide-based copolymer is not particularly limited.
It is preferably 65% by weight, more preferably 30 to 60% by weight or 35 to 55% by weight. The larger the number of maleimide-based monomer units, the better the properties such as heat resistance. In addition, when the amount of the maleimide-based monomer unit is large, the melting temperature becomes high, and it is easy to maintain the molten state until cutting, so that a water ring pelletizer that cuts the maleimide-based copolymer in the air, It is suitable for using a device such as a mist cut pelletizer that cuts in water. However, if the amount of the maleimide-based monomer unit is too large, it becomes brittle and the properties are deteriorated.

The heat-resistant thermoplastic resin preferably applicable to the production method of the present invention is a maleimide-based heat-resistant thermoplastic resin as described above, and more specifically, an aromatic vinyl resin.
Maleimide copolymer, alkyl (meth) acrylate /
Maleimide copolymer (specifically, for example, methyl (meth) acrylate / maleimide copolymer), or
Copolymers using the above-mentioned acrylonitriles at the time of polymerization of these copolymers (for example, aromatic vinyl / maleimide / acrylonitrile copolymer and alkyl (meth) acrylate / maleimide / acrylonitrile copolymer)
It is preferred that By applying to these resins, pellets having a more preferable shape, that is, a shape having no corner portion on the outer surface can be manufactured.

Among the maleimide-based copolymers, the maleimide-based copolymer containing an aromatic vinyl monomer unit and a maleimide monomer unit as essential components is particularly suitable for heat resistance, processability and impact resistance. The glass transition temperature is 130 ° C. or higher, preferably 160 ° C. or higher, by changing the composition ratio of each monomer unit.
Alternatively, a copolymer having a temperature of 180 ° C. or higher can be easily obtained.

When an aromatic vinyl monomer and another monomer are used as the other monomer (b), the amount of the monomer other than the aromatic vinyl monomer is determined according to the present invention. Is preferably 0 to 20% by weight without departing from the purpose of the above.

In the present invention, volatile components are those having volatility such as, for example, solvents, unreacted monomers, volatile by-products or impurities. Here, the solvent may be any solvent that can be generally used in solution polymerization or the like, and examples thereof include aromatic solvents such as toluene, xylene, and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; dimethyl sulfoxide; A polar solvent such as ethyl acetate;
Further, when a polymer is obtained by suspension polymerization or emulsion polymerization, water is used. The volatile by-product contained in the maleimide-based copolymer is a volatile low-molecular-weight substance generated during the reaction or a volatile impurity contained in the raw material.

After completion of the polymerization, the polymer composition containing the maleimide-based copolymer and the volatile component may be supplied (transferred) to an extruder and devolatilized in the extruder to be in a molten state or may be removed in advance. It may be supplied to an extruder after being volatilized and in a molten state.
The former is preferred because the step of re-melting is unnecessary and the number of steps is reduced, and the maleimide-based copolymer is less susceptible to thermal deterioration.

Further, as the heat-resistant thermoplastic resin, a resin other than the above-mentioned maleimide-based copolymer can be used.
For example, a super heat-resistant thermoplastic resin such as heat-resistant polycarbonate using polyarylate, polyether sulfone, polyphenylene ether, and cycloaliphatic bisphenol A can be used. Copolymers containing monomers such as maleimides, maleic anhydride, methacrylic acid, α-methylstyrene and the like whose homopolymer has a glass transition temperature of 150 ° C. or higher can also be used. A resin composition containing these resins may be used. Maleimides as a component of the heat-resistant thermoplastic resin are particularly preferable components because they easily provide high heat resistance and are excellent in compatibility, mechanical properties, and thermal stability.

The heat-resistant thermoplastic resin preferably has a glass transition temperature of 130 ° C. or higher, and more preferably a resin having a glass transition temperature of 150 to 300 ° C. [Extrusion step] The extruder is not particularly limited,
For example, a vent-type single-screw or twin-screw extruder having one or more vents sequentially arranged along the axial direction on the side surface of the cylinder may be used.

At the end of the cylinder of the extruder, an extrusion die similar to a normal extruder is provided. The extrusion die has pores for extruding a heat-resistant thermoplastic resin. The cross-sectional shape of the pore is usually circular, but various shapes such as an ellipse and a polygon other than the circle can be adopted. The pore diameter is 0.5 ~
50mm is adopted.

The temperature at the exit of the pores of the extrusion die, that is, the die temperature, is not particularly limited as long as the heat-resistant thermoplastic resin can be extruded in a molten state. The temperature of the heat-resistant thermoplastic resin at the time of extrusion is equal to or higher than the die temperature due to heat generation due to shearing force received in the extruder. The die temperature is preferably from 250 to 350C. In particular, the temperature is preferably 270 ° C or higher or 290 ° C or higher. If the temperature is too low, the heat-resistant thermoplastic resin is cooled by the extrusion die, and pellets cannot be produced stably. If the temperature is too high, the heat-resistant thermoplastic resin undergoes thermal deterioration, causing coloring and a decrease in molecular weight.

With respect to the pressure at the time of devolatilization of the polymer composition containing the heat-resistant thermoplastic resin and the volatile component, the devolatilization of the polymer composition progresses, and as the pressure is gradually decreased, the devolatilization proceeds. This is preferable because the efficiency of volatilization can be further increased.

In order to further increase the efficiency of devolatilization, an inert gas such as nitrogen, argon, helium, carbon dioxide or the like, or an inert liquid such as water or alcohol may be injected.

In the case where a heat-resistant thermoplastic resin is produced by a bulk polymerization method or a solution polymerization method, if the content of the heat-resistant thermoplastic resin in the polymer composition is to be increased after the polymerization is completed, the amount of the polymer composition is reduced. Since the viscosity increases and special equipment is required for removing heat generated during polymerization, and it is difficult to transfer the extruder to the extruder, a polymer composition containing 20 to 80% by weight of a volatile component is used. Is preferred. If the content of the volatile component of the polymer composition is below this range, the viscosity of the composition becomes too high, and handling may be difficult, and if it exceeds, the volatile component becomes too large and remains after desolvation, and remains. Volatile components may increase.

After devolatilization, the heat-resistant thermoplastic resin in the molten state is extruded from the pores of the extrusion die.

The linear velocity of the extruded heat-resistant thermoplastic resin is set to 2
It is preferably set to 0 to 70 cm / sec. In particular, 30-
60 cm / sec is preferred. If the linear velocity is too low, the heat-resistant thermoplastic resins cut after extrusion are fused to each other, and a plurality of pellets are united, and a ball or a deformed product is easily generated. As a result, the yield of the recovered pellets decreases, or a large amount of fine powder is mixed. If the linear velocity is too high, the pressure applied to the heat-resistant thermoplastic resin at the time of extrusion becomes excessive, and problems such as deterioration, coloring, and molecular weight reduction of the heat-resistant thermoplastic resin occur. [Cutting Step] Cutting is performed using a normal cutter blade or the like. By operating the cutter blade in contact with or close to the pores of the extrusion die, the molten heat-resistant thermoplastic resin immediately after extrusion can be cut.

The cutting can be performed in the air or in water. In order to cut in water, the heat-resistant thermoplastic resin extruded into water may be cut in water with the pore outlet of the extrusion die and the cutter device installed in water. The water in this case is preferably hot water.

The weight of the heat-resistant thermoplastic resin per pellet can be controlled by adjusting the cutting interval of the heat-resistant thermoplastic resin. The weight of the heat-resistant thermoplastic resin per pellet is preferably about 0.005 to 0.1 g.

The cutting interval can be changed by adjusting the linear speed of the heat-resistant thermoplastic resin extruded from the extrusion die and the operating cycle of the cutter blade or the like. With a rotary cutter blade, the operating cycle is adjusted according to conditions such as the rotation speed and the number of cutter blades installed. For example, in the case of a rotary cutter having a pair of cutter blades in the diameter direction, it is preferable to set the rotation speed of the cutter blade to 2000 to 5000 rpm. Especially, more than 2700rpm or 3000rpm
The above is preferred. If the cutting speed when cutting the heat-resistant thermoplastic resin in the molten state with the cutter blade is too high, wear and damage of the cutter blade increase. If the cutting speed is too low,
The fusion of the cut pellets is likely to occur as a lump,
It is difficult to perform stable cutting work.

If the heat-resistant thermoplastic resin is in a molten state,
The stress and strain generated at the time of cutting do not remain in the heat-resistant thermoplastic resin.

The cut end face of the heat-resistant thermoplastic resin has an effect of rounding the corner of the cut end face or trying to have a shape having the smallest possible surface area due to the surface tension of the heat-resistant thermoplastic resin in a molten state. As a result, the outer shape of the cut heat-resistant thermoplastic resin does not have a corner where the surface intersects with the ridge line, but transitions smoothly from surface to surface, or the whole is composed of a curved surface Or have a smooth outer surface. It is preferable to use a curved surface having a relatively large radius of curvature. Specifically, the shape is a spherical shape, a flat spherical shape in which a sphere is slightly crushed in one direction, a teardrop shape, a cylindrical shape with rounded corners, and the like. [Cooling Step] The cut heat-resistant thermoplastic resin is immediately cooled to obtain solidified heat-resistant thermoplastic resin pellets. Specifically, within 1 minute after cutting, preferably 10 to 3
It is preferable to cool the pellets to a temperature at which the pellets do not fuse together within 0 seconds, more preferably within 1 to 5 seconds. A specific cooling temperature is preferably from 150 to 20 ° C., which can suppress deterioration of the heat-resistant thermoplastic resin due to heat and prevent fusion of the pellets. By rapidly cooling, the heat-resistant thermoplastic resin in a molten state can be less affected by environmental conditions.

For cooling, ordinary cooling means such as air cooling and water cooling can be employed. In the case of water cooling, a method in which the cut heat-resistant thermoplastic resin is put into water can be adopted. If mist-like water or steam is sprayed on the heat-resistant thermoplastic resin, it is cooled by both water cooling and air cooling.

The cooled heat-resistant thermoplastic resin becomes pellets having substantially the same shape as the heat-resistant thermoplastic resin in the molten state after cutting. Also, at the beginning of the cooling step, the shape changes due to the surface tension and fluidity of the heat-resistant thermoplastic resin in the molten state continue.

In the cooling step, the pellet-shaped heat-resistant thermoplastic resin which has been cut into small pieces and has a large surface area and a small heat capacity is cooled, so that the cooling efficiency is increased and the resin is rapidly cooled to a predetermined temperature. As a result, thermal deterioration of the heat-resistant thermoplastic resin is reduced. [Pellet Manufacturing Apparatus] As an apparatus for performing the above-described cutting step and cooling step, a known pellet manufacturing apparatus can be used. Specific examples include a hot cut pelletizer, a water ring pelletizer, a mist cut pelletizer, an underwater pelletizer, a rotary knife pelletizer, and a centrifugal pelletizer. An appropriate manufacturing apparatus is selected according to processing conditions such as the glass transition temperature of the heat-resistant thermoplastic resin. For example, if the glass transition temperature is 13
When a heat-resistant thermoplastic resin having a temperature of 0 to 300 ° C. is used, the operability is good, the application range is wide, it is economical, and the shape of the produced pellet is good.
Water ring pelletizers, mist cut pelletizers and underwater pelletizers are preferred, and water ring pelletizers are particularly preferred.

For example, a watering pelletizer includes a rotary cutter in front of an extrusion die of an extruder, and a cylindrical casing that covers the outer circumference of the rotary cutter. Water is supplied to the inner surface of the casing at a high speed from the radiation direction, and a water layer is formed on the inner surface of the casing by the action of centrifugal force. The heat-resistant thermoplastic resin melt-extruded from the pores of the extrusion die is sequentially cut,
The cut heat-resistant thermoplastic resin is introduced into the water layer formed on the inner surface of the casing by the action of gravity or centrifugal force, and is conveyed through the water layer along the flow of water, and the heat-resistant thermoplastic resin is removed. Cooled. The time from when the heat-resistant thermoplastic resin in the molten state is cut to when water cooling is started in the aqueous layer is extremely short, and rapid and efficient cooling is performed.

The underwater pelletizer is
The front surface of the extrusion die of the extruder is placed in water, and the heat-resistant thermoplastic resin melt-extruded into water from the pores of the extrusion die is immediately cut in water. In this case, the heat-resistant thermoplastic resin in a molten state is cooled in water after cutting without contacting any air. (Heat-resistant thermoplastic resin pellets) The heat-resistant thermoplastic resin pellets produced by melt extrusion in the method and apparatus described above, as described above, the outer surface is flat spherical, the outer surface having no corners such as teardrop shape, Will have.

The ratio of the major axis represented by the length of the portion having the largest diameter to the minor diameter represented by the length of the portion having the smallest dimension is such that the major axis / minor axis = 1-5. Certain products are easy to handle and have excellent quality characteristics as a heat-resistant thermoplastic resin.

As the dimensions of the pellet, the major axis is 1 to 10 mm
Are preferable, and those having 2 to 6 mm are more preferable. A pellet that is too large may take a long time to cool or generate large thermal stress. Pellets that are too small are difficult to handle such as transport.

[0055]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment shown in FIG. 1 shows a water ring type pellet producing apparatus and a pellet producing method using the same, and uses a maleimide copolymer as a heat-resistant thermoplastic resin.

At the end of the cylinder of the extruder 10, an extrusion die 1 is provided.
2 is provided. A plurality of circular pores 22 penetrate the extrusion die 12 along the circumferential direction. Maleimide copolymer 20 in a molten state supplied under pressure by extruder 10
Is extruded from the pores 22 of the extrusion die 12.

A cutter 30 is arranged on the front surface of the extrusion die 12. The cutter 30 rotates with a pair of plate-like cutter blades 32 extending in a diameter direction supported by a rotating shaft 34.

When the cutter blade 32 rotates in a state in which the cutter blade 32 is almost in contact with the front surface of the extrusion die 12,
The maleimide-based copolymer 22 extruded from 2 is immediately cut into small lumpy pellets 24. In the cut pellets 24, the maleimide copolymer is still in a molten state. Due to the surface tension and the like of the maleimide-based copolymer, the corners of the pellets 24 are rounded, and the pellets 24 are deformed into a smooth curved surface shape, and finally try to be spherical. However, due to the external force, weight, and inertia applied to the shape during extrusion and cutting, the shape does not become a perfect sphere, but usually becomes a slightly distorted flat sphere.

The pellet 24 cut by the cutter blade 32
Moves in the outer peripheral direction due to the centrifugal force or weight of the cutter blade 32.

The outer periphery of the front surface of the extrusion die 12 has a cylindrical casing 40. High-speed water is supplied to the inner surface of the casing 40 from the outside along the radiation direction. The water moves so as to rotate in the circumferential direction along the inner surface of the casing 40, and due to centrifugal force associated with the rotation and the effect of gravity due to the inclination of the casing 40, water having a constant thickness is formed around the entire inner surface of the casing 40. The layer 42 is formed, and flows in the axial direction of the casing 40 toward the downstream side. The casing 40 is provided with a water collecting portion at an end portion farther from the extrusion die 12, and collects water flowing from the upstream side.

The pellet 24 cut by the cutter blade 32 and blown in the outer peripheral direction is
It is thrown into. The pellets 24 placed in the water layer 42 move together with the water layer 42 while undergoing a water cooling action, and are collected after being cooled to a predetermined temperature. Since an excessive deformation force or the like is not applied to the pellets 24 moving in the water layer 42 from the outside, the pellets 24 are solidified while maintaining a smooth curved surface shape close to the spherical shape.

As shown in FIG. 2, the maleimide-based copolymer pellets 24 solidified by cooling have a substantially circular planar shape (FIG. 2 (b)) and a slightly crushed vertical side shape [FIG. a)]. Major axis of the outer diameter D ₁ of the greatest points outside diameter, the outside diameter and the minor axis of the outer diameter D ₂ of the smallest point, represented by the major axis / minor axis = D ₁ / D _2.

The pellets 24 having such an outer shape without corners are less likely to be chipped or cracked during handling and generate less fine powder.

[0064]

EXAMPLES Specific examples of the present invention will be shown below, but the present invention is not limited to the following examples. In the following, “parts” means “parts by weight”. Each measured value was determined under the following conditions.

(Polymerization Reaction Rate, Polymer Composition Analysis) The amount of unreacted monomer in the obtained polymerization reaction mixture was measured by gas chromatography (manufactured by Shimadzu Corporation, apparatus name: GC-14A). From the results, the polymerization reaction rate and the polymer composition were determined.

(Weight average molecular weight) GPC (G by Tosoh Corporation)
(PC system) and in terms of polystyrene.

(Coloring degree YI of resin) A resin was dissolved in chloroform, a 15% solution was put in a quartz cell, and measured using a color difference meter (SZ- # 90, manufactured by Nippon Denshoku Industries Co., Ltd.).

(Thermal analysis of resin) TG (manufactured by Rigaku Corporation, apparatus name: TG-8110) and DSC (manufactured by Rigaku Corporation, apparatus name:
Using DSC-8230), the test was performed under the conditions of a sample of about 10 mg, a heating rate of 10 ° C./min, and a nitrogen flow of 50 cc / min.

(Measurement of Volatile Content in Resin) The measurement was carried out using gas chromatography (manufactured by Shimadzu Corporation, device name: GC-14A).

(Transparency of molded article) A turbidimeter (manufactured by Nippon Denshoku Industries Co., Ltd., device name: NDH-) was applied to a test piece (thickness 3 mm, diameter 50 mm) obtained by injection molding using a sample resin. 10
01DP), the total light transmittance was measured, and the transparency was evaluated.

Polymerization Example 1 A maleimide copolymer composition used in Example 1 was prepared.

A polymerization reactor equipped with a condenser, a stirrer and two dropping funnels was charged with 7.2 parts of styrene and 36.5 parts of toluene. The inside of the reactor was replaced with nitrogen, and the temperature was raised to 114 ° C.

Into this reactor, 0.01 part of t-butylperoxyisopropyl carbonate was added as a polymerization initiator to start the reaction, and 23.3 parts of N-phenylmaleimide prepared in advance and toluene were added. 1
5.5 parts of a dropping liquid (1) and styrene 1
Polymerization was carried out in a refluxing state while dropping liquid (2) consisting of 7.5 parts and 0.02 part of t-butylperoxyisopropyl carbonate was dropped from each dropping funnel at a uniform rate over 3.5 hours. After completion of the dropwise addition, the reaction mixture was continuously heated for another 1.5 hours, so that toluene 52.
A maleimide-based copolymer composition having a composition of 0% by weight, 5.1% by weight of styrene, and 42.9% by weight of the maleimide-based copolymer was obtained. The unreacted N-phenylmaleimide was less than 0.05% by weight and could not be detected.

The maleimide copolymer in the obtained composition was composed of 54.3% by weight of N-phenylmaleimide units and 45.7% by weight of styrene units, and had a glass transition temperature (Tg) of 206 ° C. Met.

The maleimide copolymer composition obtained in the above polymerization example was biaxially meshed with a vent type screw extruder [manufactured by Nippon Steel Works, Ltd., screw diameter (D) 120 mm, cylinder length ( L) 5460 mm, L /
D = 44.5, 4 vents (1 rear vent, 3 fore vents)], and the following examples and comparative examples were performed.
The extrusion die provided at the end of the cylinder of the extruder has a large number of pores having a diameter of 3 mmφ formed along the circumference.

Example 1 The maleimide copolymer composition obtained in Polymerization Example 1 was passed through a static mixer type heat exchanger with a gear pump and heated to 240 ° C., and was heated to 20 kg / cm ² by a pressure regulating valve. Then, the composition was supplied to an extruder in which the barrel temperature was set at 290 ° C. The degree of vacuum of the first, second and third vents of the extruder is 250 mmHg, 20 mmHg,
The volatile components were removed by operating to 20 mmHg, and 450 mm diameter dies (pores) of the extrusion die were used to remove 450
The maleimide-based copolymer in a molten state was extruded at kg / hour (linear velocity: 40 cm / sec). The temperature of the copolymer at the exit of the die was 304 ° C.

A commercially available water ring pelletizer is installed at the tip of the extruder, and has a structure schematically shown in FIG. The cutter is provided with a pair of cutter blades in the diameter direction and rotates at 3500 rpm.

The maleimide copolymer extruded from the extrusion die is cut by about 0.03 g by rotation of a cutter blade, and is introduced into the water layer of the casing. The water temperature of the aqueous layer was 40 ° C. The maleimide-based copolymer pellets cooled in the aqueous layer were carried out together with the water at the axial end of the casing, and then separated and recovered from the water.

The obtained pellets had a flat spherical shape as shown in FIG. 2, and had a major axis D ₁ = 4 mm, a minor axis D ₂ = 2 mm, and a major axis / minor axis = 2. The color tone is YI6 and the molecular weight is 1
It was 90,000. When this pellet was used for the production of a heat-resistant resin product, the generation of fine powder during handling was reduced, the work was easy, and the quality performance of the product was good.

-Polymerization Example 2- A maleimide copolymer composition used in Example 2 was prepared.

In a polymerization reactor equipped with a condenser, a stirrer and two dropping funnels, 5.0 parts of styrene, 5.0 parts of acrylonitrile, and 47.3 parts of toluene were charged, and the inside of the reactor was replaced with nitrogen. The temperature was raised to ° C.

Into this reaction vessel, 0.038 part of t-butylperoxyisopropyl carbonate as a polymerization initiator was added to start the reaction, and 16.0 parts of N-phenylmaleimide, acrylonitrile prepared in advance were prepared. A dropping solution (1) consisting of 1.0 part and 10.7 parts of toluene was added over 3 hours and 15.0 parts of styrene.
And a dropping solution (2) consisting of 0.15 parts of tert-butylperoxyisopropyl carbonate and 0.15 parts of t-butylperoxyisopropyl carbonate was dropped at a uniform rate over 3.5 hours to carry out polymerization under reflux. After completion of the dropwise addition, the reaction mixture was further heated for 5.5 hours, so that 58.0% by weight of toluene, 0.1% by weight of styrene, 0.3% by weight of acrylonitrile, and 41.5% by weight of a maleimide copolymer were obtained. % Of a maleimide-based copolymer composition. In addition, unreacted N-
Phenylmaleimide was less than 0.05% by weight and could not be detected.

The maleimide copolymer in the obtained composition was composed of 39% by weight of N-phenylmaleimide unit, 14% by weight of acrylonitrile unit and 47% by weight of styrene unit.
Having a glass transition temperature (Tg) of 1
65 ° C.

The maleimide copolymer composition obtained in the above polymerization example was biaxially meshed with a vent type screw extruder [manufactured by Nippon Steel Works Co., Ltd., screw diameter (D) 120 mm, cylinder length ( L) 5460 mm, L /
D = 44.5, 4 vents (1 rear vent, 3 fore vents)], and the following examples and comparative examples were performed.
The extrusion die provided at the end of the cylinder of the extruder has a large number of pores having a diameter of 3 mmφ formed along the circumference.

Example 2 The maleimide-based copolymer composition obtained in Polymerization Example 2 was passed through a static mixer type heat exchanger with a gear pump and heated to 240 ° C., and then was heated to 20 kg / cm ² by a pressure regulating valve. Then, the composition was supplied to an extruder in which the barrel temperature was set to 300 ° C. The degree of vacuum of the first, second and third vents of the extruder is 250 mmHg, 20 mmHg,
The volatile components were removed by operating to 20 mmHg, and 450 mm diameter dies (pores) of the extrusion die were used to remove 450
The maleimide-based copolymer in a molten state was extruded at kg / hour (linear velocity: 40 cm / sec). The temperature of the copolymer at the exit of the die was 300 ° C.

A commercially available water ring pelletizer is provided at the tip of the extruder, and has a structure schematically shown in FIG. The cutter is provided with a pair of cutter blades in the diameter direction and rotates at 3500 rpm.

The maleimide-based copolymer extruded from the extrusion die is cut by about 0.03 g by rotation of a cutter blade, and is put into an aqueous layer of a casing. The water temperature of the aqueous layer was 40 ° C. The maleimide-based copolymer pellets cooled in the aqueous layer were carried out together with the water at the axial end of the casing, and then separated and recovered from the water.

The obtained pellets had a flat spherical shape as shown in FIG. 2, and had a major axis D ₁ = 4 mm, a minor axis D ₂ = 2 mm, and a major axis / minor axis = 2. The color tone was YI25 and the molecular weight was 130,000. When this pellet was used for the production of a heat-resistant resin product, the generation of fine powder during handling was reduced, the work was easy, and the quality performance of the product was good.

-Polymerization Example 3- A maleimide copolymer composition used in Example 3 was prepared.

N-phenylmaleimide was placed in a polymerization reactor equipped with a condenser, a stirrer and two dropping funnels.
3 parts, 15.8 parts of methyl methacrylate, and 25 parts of toluene were charged, and the inside of the reaction vessel was replaced with nitrogen.
The temperature was raised to ° C.

Into this reactor, 0.004 parts of t-butyl peroxyisopropyl carbonate as a polymerization initiator was added to start the reaction, and 6.2 parts of N-phenylmaleimide prepared in advance and toluene were added. 25 parts of a dropping liquid (1), 6.0 parts of styrene and 0.0 parts of t-butylperoxyisopropyl carbonate
A dropping solution (2) consisting of 2 parts was dropped from each dropping funnel into 3.5.
The polymerization was carried out in a reflux state while dropping at a uniform rate over time. After the completion of the dropwise addition, the reaction mixture was continuously heated for another 5.5 hours to obtain 52.0% by weight of toluene,
A maleimide-based copolymer composition having a composition of 0.1% by weight of styrene, 3.0% by weight of methyl methacrylate, 0.1% by weight of N-phenylmaleimide and 46.8% by weight of a maleimide-based copolymer was obtained. .

The maleimide copolymer in the obtained composition was composed of 26.0% by weight of N-phenylmaleimide unit, 60.8% by weight of methyl methacrylate unit and 1% of styrene unit.
It consisted of 3.2% by weight and had a glass transition temperature (Tg) of 142 ° C.

The maleimide copolymer composition obtained in the above polymerization example was biaxially meshed with a vent-type screw extruder [manufactured by Nippon Steel Works Co., Ltd., screw diameter (D) 120 mm, cylinder length ( L) 5460 mm, L /
D = 44.5, 4 vents (1 rear vent, 3 fore vents)], and the following examples and comparative examples were performed.
The extrusion die provided at the end of the cylinder of the extruder has a large number of pores having a diameter of 3 mmφ formed along the circumference.

Example 3 The maleimide-based copolymer composition obtained in Polymerization Example 3 was passed through a static mixer type heat exchanger by a gear pump and heated to 240 ° C., and the pressure was adjusted to 20 kg / cm ² by a pressure control valve. Then, the composition was supplied to an extruder in which the barrel temperature was set to 260 ° C. The degree of vacuum of the first, second and third vents of the extruder is 250 mmHg, 20 mmHg,
The volatile components were removed by operating to 20 mmHg, and 450 mm diameter dies (pores) of the extrusion die were used to remove 450
The maleimide-based copolymer in a molten state was extruded at kg / hour (linear velocity: 40 cm / sec). The temperature of the copolymer at the exit of the die was 300 ° C.

A commercially available water ring pelletizer is installed at the tip of the extruder, and has a structure schematically shown in FIG. The cutter is provided with a pair of cutter blades in the diameter direction and rotates at 3500 rpm.

The maleimide-based copolymer extruded from the extrusion die is cut into about 0.03 g by rotation of a cutter blade, and is put into an aqueous layer of a casing. The water temperature of the aqueous layer was 40 ° C. The maleimide-based copolymer pellets cooled in the aqueous layer were carried out together with the water at the axial end of the casing, and then separated and recovered from the water.

The obtained pellets had a flat spherical shape as shown in FIG. 2, and had a major axis D ₁ = 4 mm, a minor axis D ₂ = 2 mm, and a major axis / minor axis = 2. The color tone is YI4 and the molecular weight is 2
It was 30,000. When this pellet was used for the production of a heat-resistant resin product, the generation of fine powder during handling was reduced, the work was easy, and the quality performance of the product was good.

Comparative Example After the maleimide copolymer composition obtained in Polymerization Example 1 was desolvated under the same conditions using the extruder of Example 1, the maleimide copolymer in a molten state was obtained. Was extruded into strands, and the strands were cut with a strand cutter while being cooled at regular intervals to form pellets.

The obtained pellets were columnar with a major axis of 3 mm and a height of 3.5 mm, and had a shape having corners. The color tone was YI10 and the molecular weight was 190,000. Also,
A large amount of powder was generated during cutting. When the pellets were used for production of a heat-resistant resin product, generation of fine powder was observed even during handling.

[0100]

According to the method of the present invention, a melt-extruded heat-resistant thermoplastic resin such as a maleimide-based copolymer is cut immediately in a molten state, and then rapidly cooled to produce pellets. Thereby, coloring, thermal deterioration, cracks, etc. do not occur, and high productivity can be obtained continuously and heat-resistant thermoplastic resin pellets can be obtained.

In particular, pellets with no corners on the outer surface are less likely to chip or crack during handling, generate less fine powder, and are easier to handle.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a manufacturing method showing an embodiment of the present invention.

FIG. 2 is a side view (a) and a plan view (b) of a manufactured pellet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Extruder 12 Extrusion die 14 Micropore 20 Maleimide copolymer 24 Pellets 30 Cutting device 32 Cutter blade 40 Casing 42 Water layer

Claims (7)

[Claims] 1. A method for producing heat-resistant thermoplastic resin pellets by melt extrusion using an extruder having an extrusion die, wherein the heat-resistant thermoplastic resin in a molten state at a glass transition temperature of 150 to 300 ° C. Extruding from the pores provided in the extrusion die, cutting the molten heat-resistant thermoplastic resin immediately after being extruded from the pores, and cooling the cut molten heat-resistant thermoplastic resin Obtaining a heat-resistant thermoplastic resin pellet in a solidified state by heating. 2. The method for producing heat-resistant thermoplastic resin pellets according to claim 1, wherein in the cooling step, the heat-resistant thermoplastic resin in a molten state is put into water and cooled. 3. The method for producing heat-resistant thermoplastic resin pellets according to claim 1, wherein in the extrusion step, the linear velocity of the heat-resistant thermoplastic resin extruded from the pores is 20 to 70 cm / sec. 4. The heat-resistant thermoplastic resin in the molten state is cut using a cutter blade rotating at 2000 to 5000 rpm along the front surface of the extrusion die. A method for producing the heat-resistant thermoplastic resin pellet according to the above. 5. A method for producing a maleimide-based heat-resistant thermoplastic resin by melt extrusion using an extruder having an extrusion die, wherein a heat-resistant thermoplastic resin containing a maleimide-based copolymer is added to the extrusion die. Extruding from the provided pores, cutting the heat-resistant thermoplastic resin in a molten state immediately after being extruded from the pores, and cooling and solidifying the cut heat-resistant thermoplastic resin in the molten state. A step of obtaining a heat-resistant thermoplastic resin pellet according to (1). 6. The maleimide-based thermoplastic resin pellet according to claim 5, wherein the maleimide-based copolymer is a maleimide-based copolymer containing 20 to 65% by weight or more of a maleimide-based monomer unit. Production method. 7. A heat-resistant thermoplastic resin pellet produced by melt extrusion, wherein the heat-resistant thermoplastic resin pellet has no corners on its outer surface and a ratio of major axis to minor axis is major axis / minor axis = 1 to 5. Plastic resin pellets.