JPH0326520A - Reactive extrusion molding method and extrusion screw for reactive extrusion molding machine - Google Patents

Abstract

PURPOSE:To secure a necessary polymerization reaction time for a monomer, and a plasticizing and kneading time for an obtained polymer, by making use of a screw kneading type extrusion molding machine whose extruding screw is constituted of only a compression part and resin melting, kneading and measuring part. CONSTITUTION:A gear pump 32 and two-part liquid mixing and delivery device 33 are arranged respectively on the lower part of vessel 30, 31 and the lower part of the gear pump 32, the bottom becomes a static mixer 34 and the delivery part is inserted into a raw material loading port 35 of an extrusion molding machine. The inside of the extrusion molding machine is provided with vent screws 36 biaxially in the different directions and there is a vacuum deaerating vent hole 37 on the upper part of the screws 36. A molding die 39 is on an end part of the extrusion molding machine. Since an extruding screw is constituted of only a compression part B and metering part C and the same is obtained by diverting an amount of a length of a feed part which has been made necessary so far to the metering part, a plasticizing and kneading period of time for a polymer obtained through polymerization can be taken sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a reactive extrusion molding method and an extrusion screw for a reactive extrusion molding machine.

[Prior Art and its Problems] In recent years, reactive extrusion has been widely used to form electric wires, pipes, tubes, and the like. In this method, the steps of polymerizing a liquid monomer to obtain a polymer, and then plasticizing and molding the obtained polymer are performed continuously in one extrusion molding machine.

By this method, it is possible to obtain a molded article of good quality under stable reaction conditions, and it is possible to reduce the number of steps and equipment space, thereby achieving an overall cost reduction.

In an extrusion molding machine used in such a reactive extrusion or shaping method, the polymerization reaction time of monomers and the plasticization kneading time of the obtained polymer usually take several tens of minutes. Therefore, in order to sufficiently polymerize the monomers and sufficiently plasticize and knead the resulting polymer, it is necessary to allow a sufficient residence time for the monomers and polymers in the extruder.

FIG. 6(a) is a front view of an extrusion screw of a conventional general thermoplastic resin extrusion molding machine, and FIG. 6(b) is a front view of a helical groove formed on the circumferential surface of the screw. It is an explanatory view showing depth and interval.

The screw 60 has a feed section A which is a resin supply section,
It consists of a compression section B and a metering section C which is a resin melting, kneading and measuring section, each of which is connected to the other, and a feed section A.
Spiral grooves are continuously formed on the circumferential surface from the metering portion C to the metering portion C at predetermined intervals. Feed part A
The extruder takes in pellets or powdered thermoplastic polymer from the hopper of the extruder and sends it to the compression section. Note that in the feed section A, the groove depth of the screw is constant. In addition, L in the figure is the screw length,
D1 screw diameter, P is helical groove spacing, h+ is feed portion helical groove depth, h. ．． represents the depth of the spiral groove in the metering part, and θ represents the helix angle of the spiral groove.

In order to ensure a sufficient residence time of the monomer and polymer within the extrusion molding machine, the ratio L/D between the screw length L and the screw diameter D may be increased. In fact, in order to perform reactive extrusion molding well, it is a necessary condition that L/D≧30.

However, most of the extrusion screws of extrusion molding machines currently on the market have an L/D ratio of 20 to 28.
belongs to. When reactive extrusion molding is performed using such an extrusion screw, the minimum necessary polymerization reaction time of monomers and plasticization kneading time of the obtained polymer cannot be obtained, which adversely affects the molded product.

As a result of extensive research, the present inventors have developed a screw kneading type extrusion or molding machine that eliminates the feed section of the extrusion screw, which was conventionally considered indispensable for extrusion molding, and is equipped with an extrusion screw that has a longer metering section instead. It has been found that the above drawbacks can be overcome by using.

The present invention has been made in view of these points, and provides an extrusion screw for a reactive extrusion molding machine that can perform reactive extrusion well, and a reactive extrusion molding using a screw kneading type extrusion molding machine equipped with this extrusion screw. The purpose is to provide a method.

[Means for Solving the Problems] The present invention involves supplying a low-molecular liquid raw material to a screw kneading type extrusion molding machine, causing a polymerization reaction in the extrusion molding machine to produce a high-molecular-weight polymer, and then In a reactive extrusion molding method for obtaining a molded article by extrusion molding the polymer while plasticizing and melting it, a screw kneading type extrusion molding machine including an extrusion screw consisting of only a compression part and a resin melt kneading measuring part. A reactive extrusion molding method characterized by using a kneading type extrusion molding machine, and an extrusion screw for a reactive extrusion molding machine characterized by comprising only a compression section and a resin melt kneading and measuring section.

FIG. 1 is an explanatory diagram showing one embodiment of an extrusion screw for a reactive extrusion molding machine of the present invention. In the figure, 10 is an extrusion screw, which consists of a compression part B and a metering part C, which are connected to each other. Further, the circumferential surface of the extrusion screw 10 from the end of the compression part B to the end of the metering part C via the connecting part between the metering part C and the compression part B has a spiral shape continuously and at predetermined intervals. A groove is formed in the Here, h.
is the compression part spiral groove depth, h. is the metering part helical groove depth, and in the compression part B, the compression part helical groove depth h. is gradually shallower from the end of the compression section B toward the metering section C, that is, the helical groove depth h. becomes shallower from the end of the compression part B toward the metering part C, and becomes equal to the metering part helical groove depth h1 at the part connected to the metering part C. Note that the depth of the spiral groove of the metering part C is h. is constant.

FIG. 2 is an explanatory diagram showing another embodiment of the extrusion screw for a reactive extrusion molding machine of the present invention. The interval Pm between the shaped grooves is formed so that it gradually narrows from the connecting part of the compression part B and the metering part to the end of the metering part C. That is, the interval P between the spiral grooves of the metering section. However, compression section B and metering section C
It becomes narrower from the connecting part to the end of the metering part C. Note that the interval between the spiral grooves in the compression part is P. is constant.

The shape of the extrusion screw is such that the depth of the helical grooves in the compression part is reduced as shown in Fig. 1, and the shape of the extrusion screw in which the interval between the helical grooves in the metering part is reduced as shown in Fig. 2 is the reactive extrusion molding method. It is particularly suitable as an extrusion screw for a screw kneading type extrusion molding machine.

The extrusion screw of the present invention does not have a feed section, which is conventionally considered indispensable for extrusion screws. This is because in the reactive extrusion molding method, the raw material is in a liquid state, so a liquid transport pump can be used when supplying the raw material to the extrusion molding machine, thereby eliminating the need for a feed section. Here, examples of the liquid transport pump include a gear pump and a snake pump. In the present invention, the length of the feed section, which was conventionally required as an extrusion screw for a screw kneading type extrusion molding machine, is diverted to the metering section, thereby increasing the length of the metering section. The method is designed to allow sufficient time for plasticization and kneading of the polymer obtained.

The ratio CR of the cross-sectional area of the tip of the screw compression part to the cross-sectional area of the metering part in the extrusion screw of the present invention is expressed by the following formula, and is preferably 1.15 or more.

CR- (h.(D-h.)xP.l/(h..(
D-h. )xP-1 where h. is the compression groove depth, P.
is the compression part groove interval, P. is the metering section groove spacing.

In addition, the length of the compression part in the extrusion screw is 3XD
It is preferable that it is above.

This is because if the ratio CR between the cross-sectional area of the tip of the screw compression part and the cross-sectional area of the metering part and the length of the compression part do not satisfy the above conditions, the liquid raw material tends to stay in the compression part, and the reaction extrusion This is because it adversely affects the molding method.

The metering section preferably has various mixing mechanisms such as dalmage, barrier type, and vinyl type in order to ensure that the polymerization reaction of the monomers is sufficiently carried out. Particularly preferred are those provided with vent holes to remove residues.

The extruder to be used is preferably a twin-screw extruder in terms of prevention of slippage in the extruder for liquid raw materials, reaction yield during polymerization, and the like.

Next, the reactive extrusion molding method of the present invention will be explained.

FIG. 3 is an explanatory diagram showing an example of an extrusion molding machine for carrying out the reactive extrusion molding method of the present invention.

In the figure, 30 and 31 are containers for holding monomers that have been heated and liquefied. Here, it is preferable to raise the temperature of the liquid raw material to around the cylinder set temperature of the extrusion molding machine to an extent that does not adversely affect its reactivity. Containers 30 and 3
A gear pump 32 is arranged below the container 1 and is connected to the bottom of each of the containers 30 and 31 by a conduit. Further, a two-liquid mixing and discharging device 33 is disposed below the gar bombs 32, and is connected to each gar bomb 32 by a conduit. Two-liquid mixing and discharging device 33
A static mixer 34 is connected to the bottom. The discharge part of the static mixer 34 is inserted into the raw material input port 35 of the extrusion molding machine. A two-wheeled, opposite-direction bent screw 36 is inserted into the extrusion molding machine. There is a vent hole 37 for vacuum degassing above the metering part of the biaxial and opposite direction vent screw 36. A molding die 39 is attached to the end of the extrusion molding machine for coating the molded product 38 with the polymer kneaded inside the extrusion molding machine. Using such an extrusion molding machine, the molding temperature is 1
Reactive extrusion is carried out at 80 to 230°C.

Basically, polymers that can be applied to the reactive extrusion molding method may be any polymer that can carry out the synthesis reaction by means such as stirring, mixing, and heating, that is, by the functions possessed by the extrusion molding machine.

Examples of such compounds include active hydrogen-containing compounds obtained by mixing polyether polyols, polyester polyols, and the like with diols such as 1,4-butanediol and hydroquinone-bis(β-hydroxyethyl) ether;
Polyurethane elastomer obtained by addition polymerization reaction with polyisocyanate such as , 4'-diphenylmethane diisocyanate Polymethyl methacrylate obtained by addition polymerization reaction of methyl methacrylate monomer in the presence of a catalyst such as benzoyl peroxide, polymerization of trioxane Examples include poly-1oxymethylene obtained by the reaction and nylon-6 obtained by the ionic polymerization reaction of ε-caprolactam.

Further, if necessary, a flame retardant, an auxiliary agent, a coloring agent, and a foaming agent may be mixed into the raw material within a range that does not impair the effects of the present invention.

[Function] The extrusion screw of the present invention consists of only a compression section and a metering section, and the length of the conventionally required feed section is diverted to the metering section.
For example, conventional L/D was 20 to 28, but 30
It corresponds to 40 to 40, and enough time can be taken for plasticizing and kneading the polymer obtained by polymerization.

In addition, since the reactive extrusion molding method of the present invention is carried out using an extrusion screw consisting only of a compression section and a metering section,
Sufficient residence time of the monomer and polymer within the extrusion molding machine can be ensured.

As a result, sufficient polymerization reaction time and plasticization kneading time can be ensured, and polymerization, kneading, and molding can be performed continuously in an extrusion molding machine. Therefore, a reactive extrusion molded product having stable and excellent properties can be easily obtained.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

Example First, 100 ffi parts of polytetramethylene glycol, 30 parts by weight of decabromodiphenyl ether as a flame retardant, and 10 parts by weight of antimony dioxide were kneaded using a triple roll to obtain a liquid mixture. Next, 140 parts by weight of the obtained liquid mixture and 18 parts by weight of 1,4-butanediol
parts by weight and 65.5 parts by weight of 4,4'-diphenylmethane diisocyanate were fed into the hopper of a twin-screw vented extruder as shown in FIG. 3 equipped with an extrusion screw as shown in FIG. The twin-screw vent type extrusion molding machine used was D-30φ, L/D-24, CR-2.2.
Met.

FIG. 4 is a plan view of the biaxial, counter-venting screw of the present invention. This screw consists of a compression section B on the raw material inlet side and a metering section C with a dungeon on the forming die side. Here, the spiral groove of the compression part B is 4
The pitch and metering section C are 20 pitches, and the depth of the groove is formed to become gradually shallower from the end of the compression section toward the metering section. Also, the compression part groove depth h. is 6.5, metering groove depth h. is 2.5 mm.

Reaction extrusion molding is performed using this extrusion molding machine, and polyurethane elastomer is molded to a thickness of 0.6 mm on a core material with a diameter of 0.8φ.
A molded body was prepared by coating with The extrusion molding conditions are as follows:
The temperature set during forming is 180 to 220°C, the screw rotation speed is 10 Orpm, and the nipple of the forming die is 0.5°C.
81+am, the die of the molding die is 2. It was Onn.

The external appearance, tensile strength, elongation, and flame retardance of the produced extruded product were examined. The results are shown in Table 1 below. In addition, the appearance is judged visually, and the tensile strength and elongation are 2 0 0 + n +
A tensile test was conducted on the core material at a speed of */sin, and flame retardancy was determined using the VW-1 test method of the UL standard.

Comparative Example The same raw materials as in the example were used, except that the conventional extrusion screw shown in FIG. 5 was used.
Polyurethane elastomer is applied to the core material, which is 8φ, to a thickness of 0.
A molded article was prepared by coating with 6 pieces.

FIG. 5 is a plan view of a conventional biaxially vented screw in different directions. This screw consists of a feed section A on the raw material input side, a compression section B, and a metering section C with a dullage on the forming die side. Here, the spiral groove in the feed section A had 8 pitches, the spiral groove in the compression section B had 4 pitches, and the spiral groove in the metering section C had 12 pitches.

In addition, the feed section groove depth h. is 6. 51++1%
h. m was 2.5 mm.

The appearance, tensile strength, elongation, and flame retardance of the produced extruded product were examined in the same manner as in the examples. The result' is shown in the first section below.
Also listed in the table.

Table 1 As is clear from Table 1, the extrusion molded articles coated by extrusion using the extrusion screw of the present invention were excellent in appearance, mechanical strength, and flame retardancy. On the other hand, those using conventional extrusion screws were unsatisfactory in terms of appearance, mechanical strength, and flame retardancy.

[Effects of the Invention] As explained above, the reactive extrusion molding method using the extrusion screw for a reactive extrusion molding machine of the present invention makes it possible to obtain a reactive extrusion molded article having excellent properties.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the extrusion screw for a reactive extrusion molding machine of the present invention, FIG. 2 is an explanatory diagram showing another embodiment of the extrusion screw for a reactive extrusion molding machine of the present invention, and FIG. An explanatory diagram showing an example of an extrusion molding machine for carrying out the reactive extrusion molding method of the invention, FIG. 4 is a plan view of a biaxial oppositely bent screw equipped with an extrusion screw of the invention, and FIG. 5 is a plan view of a conventional biaxial extrusion molding machine. Top view of the different direction vent screw, Figure 6 (a
) is a front view of an extrusion screw of an extrusion molding machine equipped with a conventional extrusion screw, and FIG. 6(b) is an explanatory diagram showing the depth and spacing of the spiral grooves formed on the circumferential surface of the same screw. 10.20.60...Extrusion screw 30,31.
... Container, 32... Gear pump, 33... Two-liquid mixing and discharging device, 34... Static mixer 35...
- Raw material inlet, 36... Biaxial different direction vent screw 37... Vent hole, 38... Molded product, 39...
molding die.

Claims (2)

[Claims] (1) A low-molecular liquid raw material is supplied to a screw kneading type extrusion molding machine, and a polymerization reaction is performed in the extrusion molding machine to increase the molecular weight to produce a polymer, and then the polymer is extruded while being plasticized and melted. In the reaction extrusion molding method for molding and obtaining molded products, it is recommended to use a screw kneading type extrusion molding machine equipped with an extrusion screw consisting only of a compression section and a resin melt kneading and measuring section. Characteristic reactive extrusion molding method. (2) An extrusion screw for a reactive extrusion molding machine, characterized in that it consists only of a compression section and a resin melt kneading and measuring section.