JPH05230204A - Continuous production of polyamide resin - Google Patents

Abstract

PURPOSE:To obtain at good efficiency a specified crystalline copolyamide excellent in heat resistance, etc., and having low water absorptivity by forming a lower condensate by continuous polymerization and subjecting this condensate to a continuous treatment for increasing its molecular weight in a melter. CONSTITUTION:A process for producing a crystalline copolyamide comprising hexamethyleneterephthalamide units (A) of formula I and any one kind of structural units selected from among hexamethyleneisophthalamide units (B) of formula II, hexamethyleneadipamide units (C) of formula III and capramide units (D) of formula IV in a comonomer ratio (by weight) of A/B of 55/45-80/20, A/C or 20/80-80/20 or A/D of 55/45-90/10, which process comprises forming a lower condensate of a relative viscosity of 1.01-1.6 as measured in a 1% sulfuric acid solution at 25 deg.C by continuous polymerization at 150-350 deg.C and subsequently subjecting this condensate to a continuous treatment for increasing its molecular weight in a melter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous method for producing a polyamide resin, and more particularly to a method for producing a heat-resistant polyamide resin having low water absorption suitable for automobile parts and electric / electronic parts.

[0002]

2. Description of the Related Art Polyamides have been widely used in the fields of automobiles, electric and electronic fields, etc. by utilizing their excellent properties as engineering plastics.

Conventionally, nylon 6 and nylon 66 reinforced with glass fiber have been used for these molded products (Japanese Patent Laid-Open No. 59-161461). However, due to recent technological innovation, the temperature rise of the engine room of automobiles and With the progress of microelectronics, there has been a demand for a material for an ultra-thin molded product that can withstand use in a higher temperature atmosphere. However, the melting points (Tm) of nylon 6 and nylon 66 are 220 ° C. and 260 ° C., respectively, and the limits of the heat distortion temperature are only the melting points even when reinforced with glass fiber.

Recently, many copolyamide resin compositions containing terephthalic acid and isophthalic acid, or glass fiber reinforced products thereof have been proposed as copolyamide resin compositions that can withstand use under these high temperature atmospheres. JP-A-59-161428, JP-A-59-155426,
(JP-A-59-53536, JP-A-62-156130)
. As a production method, a method of performing a polymerization reaction in a solid state from a nylon salt to a polymer has been proposed (JP-A-62-20527).

[0005]

However, these terephthalic acid- and isophthalic acid-containing copolyamide resin compositions have a high melt viscosity when the number of terephthalic acid component units is large, and discharge is impossible by a usual melt polymerization method. Since the melting point of the polymer is close to the thermal decomposition temperature of the polymer, it has been decomposed or deteriorated during melt polymerization. In addition, the method of carrying out the polymerization reaction in the solid state from the nylon salt to the polymer is
There is a problem that the composition of the polymer is not stable.

[0006]

In view of the above circumstances, the present inventors have found that the polyamide resin has a high rigidity and a high heat distortion temperature sufficient to withstand use in a high temperature atmosphere, is inexpensive, and has low water absorption. As a result of diligent studies on a method for stably producing a composition, a low-order condensate is continuously polymerized, and the low-order condensate is efficiently and stably produced by continuously increasing the degree of polymerization in a short time in a melting machine. The present invention has been achieved by finding that a polymer having a polymerization degree is obtained. That is, the present invention provides (1) a repeating unit (I) a hexamethylene terephthalamide unit represented by the following structural unit,

[Chemical 5] And any unit selected from the following repeating units (II) to (IV), (II) a hexamethylene isophthalamide unit represented by the following structure,

[Chemical 6] (III) a hexamethylene adipamide unit represented by the following structural unit,

[Chemical 7] (IV) a caproamide unit represented by the following structural unit,

[Chemical 8] And the copolymerization ratio is (I) / (II) = 55 by weight.
/ 45 to 80/20 or (I) / (III) = 20/8
0-80 / 20 or (I) / (IV) = 55 / 45-9
In producing the crystalline copolyamide in the range of 0/10, the relative viscosity (ηr) of the 1% sulfuric acid solution at 25 ° C. is from 1.01 to 1.10 under the conditions of 150 ° C. to 350 ° C.
Characterized in that the low-order condensate satisfying the condition 6 is continuously polymerized, and then the low-order condensate is continuously polymerized with a melting machine.
It is a continuous production method of polyamide resin.

The crystalline copolyamide of the present invention is any one selected from (I) hexamethylene terephthalamide unit, (II) hexamethylene isophthalamide unit, (III) hexamethylene adipamide unit and (IV) caproamide unit. And a copolymerization ratio of (I) / (II) is 55 / by weight.
45-80 / 20 (hereinafter referred to as 6T / 6I copolyamide) or (I) / (III) copolymerization ratio by weight of 20/80 to 80/20 (hereinafter referred to as 6T / 66 copolyamide). Alternatively, the copolymerization ratio of (I) / (IV) is in the range of 55/45 to 90/10 (hereinafter referred to as 6T / 6 copolyamide) in weight ratio.

According to the invention, the copolymerization ratio of 6T / 6I is 55 / 45-80 / 20, preferably 60 / 40-8.
It should be 0/20, and more preferably 60/40 to 70/30. The copolymerization ratio of 6T / 66 is 20/80 to 80/20, preferably 35/65.
~ 70/30, more preferably 40/60 to 60/40
Must be within the range. The copolymerization ratio of 6T / 6 is 55/45 to 90/10, preferably 60/4.
0-85 / 15, more preferably 60 / 40-80 / 2
It must be in the 0 range. 6T / 6 here
The copolymerization ratios of I, 6T / 66 and 6T / 6 copolyamide relate to crystalline copolyamides having a polymer melting point in the range of approximately 270 ° C to 340 ° C. 6T /
When the copolymerization ratios of 6I, 6T / 66 and 6T / 6 are less than 40/60, 20/80 and 55/45, respectively, the polymer melting point is lowered, so that heat resistance such as heat distortion temperature is lowered, which is preferable. Absent. Also, 6T / 6I, 6T
The copolymerization ratio of / 66 and 6T / 6 is 80/2, respectively.
When it is more than 0, 80/20, 90/10, the melting point of the polymer becomes high and the heat resistance is improved, but the processing temperature becomes high and the polymer is thermally decomposed, which is not preferable. The degree of polymerization of the crystalline copolyamide is not particularly limited, and the relative viscosity (ηr) of a 1% sulfuric acid solution at 25 ° C. is usually 1.5 to 5.
Those at 0 can be used arbitrarily.

The low-order condensate of the present invention is prepared by continuously supplying a monomer, an aqueous solution of a salt, a concentrate of the aqueous solution and one or more salts to a pressure-type polymerization kettle and heating them at 150 ° C. to 350 ° C. under stirring conditions. can get. In order to improve the efficiency of continuous polymerization, it is preferable that the raw material mixed aqueous solution is concentrated and charged to 50% or more, preferably 65% or more.

The reaction temperature must be 150 ° C to 350 ° C, preferably 180 ° C to 330 ° C, more preferably 190 ° C to 320 ° C. If the reaction temperature is lower than 150 ° C., the reaction time becomes long, which is not preferable, and if the reaction temperature is higher than 350 ° C., the viscosity of the low-order condensate becomes too high and discharge of the low-order condensate becomes difficult. However, a low-order condensate is deposited and discharge becomes impossible, which is not preferable.

The pressure for producing the low-order condensate of the present invention is usually 0 to 200 kg / cm ² -G, preferably 5 to 1
70 kg / cm ² -G, more preferably 10 to 150 kg
/ Cm ² -G is operated. The low-order condensate gives a significant freezing point depression due to the presence of a small amount of water.
It can be discharged from the polymerization kettle in a molten state at a temperature of 150 ° C to 350 ° C.

The relative viscosity (ηr) of the low-order condensate of the present invention must be 1.01 to 1.6, preferably 1.0 to 1.5, and more preferably 1.01 to 1. It must be in the range of 0.4. Relative viscosity (ηr) is 1.0
When it is lower than 1, it is not preferable because the composition ratio may be changed in the step of increasing the degree of polymerization by melting or the degree of increase in polymerization may be insufficient. Further, if the relative viscosity is larger than 1.6, the melt viscosity of the low-order condensate becomes too high, which causes ejection failure, or the low-order condensate is deposited, which causes ejection failure, which is not preferable. Here, ηr of the low-order condensate
Is removed by extraction and volatilization until the content of unreacted raw material components becomes 2% or less, and then subjected to measurement.

The apparatus for producing the low-order condensate of the present invention is not particularly limited, and known ones such as a complete mixing type reaction vessel and a plug flow type reaction vessel can be used. If necessary, a multi-tank system can be used.

In the usual polyamide polymerization, the total amount of COOH groups contained in the monomer and the salt and the total N are contained.
It is common to charge the raw materials so that the amount of H ₂ groups becomes equal, but in the present invention, it is preferable to prepare a low-order condensate having many COOH groups by adding an excess of dicarboxylic acid component at the time of charging the raw materials. A preferable charging ratio is to charge the dicarboxylic acid component in an excess of 0 to 10 mol% with respect to the total number of moles of the constituent monomer and the total number of moles of the dicarboxylic acid component unit and the diamine component unit of the salt, and more preferably. 0.3 ~
It is 8 mol%. If it exceeds 10 mol%, it is difficult to increase the degree of polymerization in the melting machine, which is not preferable. The dicarboxylic acid component is not particularly limited, but examples thereof include aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aromatic dicarboxylic acids such as terephthalic acid isophthalic acid. Preferred are isophthalic acid and terephthalic acid,
Especially preferred is terephthalic acid.

In order to facilitate the control of the degree of polymerization of the low-order condensate and the control of the degree of polymerization by increasing the melt degree of polymerization, it is effective to add a degree of polymerization regulator. As the polymerization degree regulator, a monoamine compound and a monocarboxylic acid compound are usually used, but benzoic acid and stearic acid are preferable, and benzoic acid is particularly preferable. The addition amount of the degree of polymerization modifier is 0 to 0.1 times, and preferably 0.0001 to 0 times the mole number of the constituent monomer and the total mole number of the dicarboxylic acid component unit and the diamine component unit of the salt. It is used in a molar amount of 0.05 times.

The method of continuously increasing the degree of polymerization of the low-order condensate of the present invention by a melter is a method of continuously increasing the degree of polymerization by melt-extruding the low-order condensate using a melter. ..

The method of supplying the low-order condensate to the melter is not specified except that it is continuous. For example, a polymerization kettle may be directly connected to the melter, or the low-order condensate discharged from the polymerization kettle may be flushed. After removing the volatile components, a method of supplying the volatile components to the melting machine can be used.

The resin temperature in the melting machine is 280 ° C to 360 ° C.
The range of ° C is preferred.

As the melting machine, a general-purpose melting machine such as an extruder or a kneader can be used, but a twin-screw extruder and a twin-screw kneader are preferable.

The residence time in the melting machine is not particularly limited, but it is preferably 1 minute or longer, particularly preferably 2 minutes or longer. A short residence time is not preferable because the degree of polymerization cannot be effectively increased. It is also effective to use two or more melting machines in series in order to prolong the residence time and increase the degree of polymerization. Although the presence of the phosphorus-based catalyst is effective for increasing the degree of polymerization, it has a drawback that the heat resistance of the obtained polyamide resin is impaired, and it is better not to add it here.

If necessary, the polyamide resin having a high degree of polymerization may be solid-phase polymerized to further increase the degree of polymerization.

A filler is preferably added to the polyamide resin obtained in the present invention. Fillers include glass fibers or beads, talc, kaolin, wollastonite, mica, silica, alumina, diatomaceous earth, clay, gypsum, red iron oxide, graphite, titanium dioxide, zinc oxide, copper, stainless steel, etc. Inorganic compounds in the form of powder or plate, other polymer fibers (carbon fibers), etc., and preferably glass fibers. As the glass fiber, glass fiber is generally used as a reinforcing agent for thermoplastic resin or thermosetting resin, but particularly preferred is a diameter of 3 to
Examples include glass rovings, glass chopped strands, and glass yarns made from strands of continuous long fibers of about 20 μm. The blending ratio of such a filler needs to be in the range of 0 to 200 parts by weight with respect to 100 parts by weight of the polyamide, preferably more than 0 and 150 parts by weight, particularly preferably 10 to 100 parts by weight. Is. When the blending ratio of the filler exceeds 200 parts by weight, the fluidity at the time of melting is deteriorated, it is difficult to injection-mold a thin molded product, and the appearance of the molded product is deteriorated, which is not preferable.

There is no particular limitation on the method of adding the filler to the crystalline copolyamide of the present invention, and any known method can be used. A specific example of the compounding method is a method in which a filler is dry-blended with crystalline copolyamide pellets, and the resulting mixture is melt-kneaded with a single-screw or twin-screw extruder. When the degree of polymerization is increased by an extruder, a method of side feeding in the middle of the extruder is preferable because of high production efficiency.

In the present invention, when the low-order condensate is produced,
Melt high polymerization degree, compound or molding process, etc.
If necessary, a catalyst, a heat resistance stabilizer, a weather resistance stabilizer, a plasticizer, a release agent, a lubricant, a crystal nucleating agent, a pigment, a dye, another polymer and the like can be added.

From the viewpoint of productivity, it is more preferable to carry out the high polymerization degree and the compound simultaneously or continuously in the melting machine.

To improve the color tone of the polyamide resin, it is effective to add an antioxidant at the time of polymerization or at the time of increasing the degree of polymerization in the melt. Particularly, the addition of an antioxidant such as sodium hypophosphite and a hindered phenol antioxidant is effective. Addition is preferred.

[0027]

The present invention will be described in more detail with reference to the following examples. The various properties in the examples and comparative examples were measured by the following methods.

1) Melting point (Tm) Samples 8 to 10 using DSC (PERKIN-ELMER7 type)
Let (T) be the temperature at which the maximum value of the melting curve obtained by measuring mg at a temperature rising rate of 20 ° C./min. Sample 8-
10 mg is heated at a temperature rising rate of 20 ° C / min to obtain T + 20 ° C.
For 5 minutes, and then at a temperature decrease rate of 20 ° C / min for 3 minutes.
After cooling to 0 ° C and holding at 30 ° C for 5 minutes, 20
Heat up to T + 20 ° C. at a heating rate of ° C./min. The maximum value of the melting curve at this time was defined as the melting point (Tm).

2) Tensile Strength It was measured according to ASTM-D638.

3) Bending strength It was measured according to ASTM-D790.

4) Flexural Modulus Measured according to ASTM-D790.

5) Izod impact strength It was measured according to ASTM-D256. 6) Heat distortion temperature (HDT) It was measured according to ASTM-D648, load 4.6 kgf / cm ² and load 18.6 kgf / cm ² . Example 1 A raw material aqueous solution having a composition ratio of 50% shown in Table 1 was continuously supplied to a 30 L complete mixing type polymerization machine, and the internal temperature was 240 ° C. and the internal pressure was 1
The low-order condensate was continuously polymerized under the conditions of 8 kg / cm ² -G and a residence time of 60 minutes. The low-order condensate was flashed to continuously remove volatile matter, and then continuously increased in polymerization degree with a twin-screw extruder with 44 mmφ and L / D = 42. The internal temperature of the extruder was set to 320 ° C., and the average residence time was set to 5 minutes. The extruder was provided with a vent port to remove water generated by the reaction. Ηr of the obtained polyamide resin was 2.8, and a sufficiently high degree of polymerization was achieved.

Next, from the side feeder of the extruder, 65 parts by weight of glass fiber chopped strands having a length of 3 mm and a diameter of 13 μm were added to 100 parts by weight of the resin.
Then, the compound of glass fiber and the high degree of polymerization were simultaneously performed. This mixture was molded by an injection molding machine to prepare a test piece. Table 1 shows the results of evaluation of the obtained test pieces.

Examples 2 to 5 Polyamide resins were produced in the same manner as in Example 1 except for the conditions shown in Table 1. The results are shown in Table 1.

In each of the methods of the examples, a polyamide resin having a high degree of polymerization was stably and efficiently obtained, and the physical properties of the molded product were also excellent.

Comparative Examples 1 and 2 Polyamide resins were produced in the same manner as in Example 1 except that the raw material composition ratio was out of the scope of the present application, except for the conditions shown in Table 1. The results are shown in Table 1. Those having a low 6T content (Comparative Example 1) could not obtain the low water-absorption heat-resistant polyamide resin targeted by the present invention, and those having too much 6T content (Comparative Example 2).
Did not foam a stable polymerized polymer having a high degree of polymerization.

Comparative Example 3 The polymerization temperature range of the low-order condensate was outside the scope of the present invention.
The same method as in Example 1 was carried out except for the conditions shown in Table 1.
Ηr of the low-order condensate was less than 1.01 and could not be recovered as the low-order condensate.

[0038]

[Table 1]

[0039]

INDUSTRIAL APPLICABILITY The crystalline copolyamide obtained according to the present invention is not only high in rigidity and heat distortion temperature but also low in water absorption and good in moldability, so that it is particularly used as a material for automobile parts and electric / electronic parts. Suitable as

Claims (1)

[Claims] (1) Repeating unit (I) Hexamethylene terephthalamide unit represented by the following structural unit: And any unit selected from the following repeating units (II) to (IV), (II) a hexamethylene isophthalamide unit represented by the following structural unit, (III) a hexamethylene adipamide unit represented by the following structural unit: (IV) a caproamide unit represented by the following structural unit, And the copolymerization ratio is (I) / (II) = 55 by weight.
/ 45 to 80/20 or (I) / (III) = 20/8
0-80 / 20 or (I) / (IV) = 55 / 45-9
In producing the crystalline copolyamide in the range of 0/10, the relative viscosity (ηr) of the 1% sulfuric acid solution at 25 ° C. is from 1.01 to 1.10 under the conditions of 150 ° C. to 350 ° C.
A continuous production method of a polyamide resin, which comprises continuously polymerizing a low-order condensate satisfying 6 and then continuously increasing the degree of polymerization of the low-order condensate with a melting machine.