HK1162551B - Method for preparing polyarylene sulfide - Google Patents

Description

Process for preparing polyarylene sulfide

Technical Field

The present invention relates to a method for preparing polyarylene sulfide (hereinafter, referred to as "PAS"), and more particularly, to a method for preparing PAS, in which a polymerization terminator is added to reactants to reduce the iodine content of PAS and enhance thermal stability.

Background

Currently, PAS, a typical Engineering Plastic (Engineering Plastic), is required in a large amount as a material for high temperature and corrosive environments and electronic products due to its properties of heat resistance, chemical resistance, flame resistance and electrical insulation. The coating is mainly used for computer parts, automobile parts, protective coatings of corrosive chemical contact parts, chemical-resistant industrial fabrics and the like.

Currently, the only PAS available on the market is polyphenylene sulfide (hereinafter referred to as "PPS"). At present, PPS is industrially synthesized by reacting p-dichlorobenzene (p-dichlorobenzyne, hereinafter referred to as "pDCB") and sodium sulfide as component materials in a polar organic solvent such as N-methyl pyrrolidone. This process is known as the "Macullum process" (Macullum process), the basic procedure of which is disclosed in U.S. Pat. Nos. 2,513,188 and 2,583,941. Several polar solvents have been suggested, but the most commonly used is N-methylpyrrolidone. In this step, a dichloroaryl compound (dichloro aromatic compound) was used as a raw material, and sodium chloride (NaCl) was obtained as a by-product.

The PPS produced in the Macallum process has a molecular weight of about 10,000-40,000 and a low melt viscosity of less than 3,000 Poise (Poise), and is not large. To obtain higher melt viscosities, PPS is typically subjected to a curing process that includes heating at a temperature below the melting temperature Tm and exposure to oxygen. At this time, the melt viscosity is increased to a generally desired level by oxidation, crosslinking (crosslinking), polymer chain extension (extension), or the like.

However, PPS obtained in the conventional Macullum process has the following major disadvantages.

First, the use of sodium sulfide as a supply of sulfur required in the polymerization reaction can produce large amounts of by-product metal salts such as sodium chloride in the polymer product. Thus, even after washing out of the polymer product, the residual metal salts contained in the polymer product reach several thousand ppm, which not only increases the electrical conductivity of the polymer but also causes corrosion of processing machines and problems in spinning the polymer into fibers. From the manufacturer's point of view, when sodium sulfide is used as a component material, the yield of sodium chloride as a final by-product reaches 52% relative to the weight of the charged material, and even if it is recovered, it is uneconomical, and thus it becomes a waste.

Second, the properties of the polymer product are adversely affected during curing. The oxygen-driven oxidation and crosslinking reaction darkens the polymer product, becoming more brittle in mechanical properties (brittlenes).

Finally, as with all solution polymerization polymers, the final PPS product is in a very fine powder form. This results in a decrease in apparent density, thereby causing inconvenience in transportation and inconvenience in processing for preparing products.

In addition to the Macallum process, other novel processes are proposed in U.S. Pat. nos. 4,746,758 and 4,786,713 and other related patents. These patents suggest that PAS is prepared without using any polar solvent by directly heating diiodo compounds and solid sulfur (solid sulfur) instead of dichloride compounds and metal sulfides (metalsulfide) used in the prior art methods. The method comprises two steps of iodination and polymerization: an iodination step to react aryl compounds with iodine to form diiodo compounds; the polymerization step reacts the diiodo compound with solid sulfur to obtain PAS of high molecular weight. During this reaction, iodine appears in vapor form, which is recovered and reacted again with the aryl compound. Thus, iodine is essentially a catalyst in this reaction.

The method can solve the problems of the conventional method. First, since the by-product is iodine, the conductivity is not increased as much as that of the metal salt, and it can be easily recovered from the reactant, so that the content thereof in the final product can be easily reduced to be lower than that of the metal salt in the conventional method. The recovered iodine can be reused in the iodination step, and thus almost the amount of waste can be removed. Second, the polymerization step does not use a solvent, and thus can provide a PAS product in pellet (pellet) form like a conventional polyester product, and can avoid the problems occurring in the use of the powder form products of the prior art. Finally, the process greatly increases the molecular weight of the final PAS product over conventional processes, thus eliminating the need for a curing process that results in deterioration of the product properties.

However, this approach has two major problems to solve. First, residual iodine in molecular form is corrosive, and even small amounts of iodine in the final PAS product adversely affect the processing machinery. Second, the use of solid sulfur in the polymerization step may result in the introduction of disulfide bonds (disulfide links) in the final PAS product, deteriorating the thermal properties of the product, including the melting temperature.

Therefore, research is needed to develop a method capable of efficiently preparing polyarylene sulfide having excellent properties such as thermal resistance, chemical resistance and mechanical strength while not generating unnecessary metal salts and significantly reducing the iodine content causing machine corrosion.

Disclosure of Invention

Problems to be solved by the invention

It is an object of the present invention to provide a method for preparing polyarylene sulfide having a low iodine content and good thermal stability.

It is another object of the present invention to provide a polyarylene sulfide having a low iodine content and good thermal stability.

It is still another object of the present invention to provide a molded article, film, sheet or fiber composed of the PAS resin.

Means for solving the problems

The present invention provides a method for preparing polyarylene sulfide, wherein the PAS is prepared by polymerization of reactants including di-iodo aromatic compound and sulfur compound, the method further comprising adding diphenyl disulfide in an amount of 0.01-10.0 wt.% relative to the weight of polyarylene sulfide to the reactants to form polyarylene sulfide having a melting temperature of 265-320 ℃.

The present invention also provides polyarylene sulfide prepared by the above method and having a melting temperature of 265 ℃ and 320 ℃ and a molded article using the same.

Detailed Description

The present invention will be described in more detail below.

The present inventors have noted the problems associated with the use of conventional polymerization inhibitors and have focused on solutions based on chemical methods. The reason for the removal of iodine from the final polymer product is not only the corrosive nature of iodine but also the economic aspects. The way in which iodine enters the polymer in the above novel process is two: in one case, the iodine molecule is directly included in the polymer; another case is where the iodine atom is bonded to an aryl group of the polymer. The present invention focuses on the solution of the latter problem, since the former solution depends mainly on the equipment or conditions of the polymerization reaction.

The present invention relates to a process for preparing PAS in a manner different from the existing industrial process by adding diphenyl disulfide (hereinafter, referred to as "PDS") as a polymerization terminator while maintaining the amount of residual iodine in the final polymer at a constant level or decreasing to a certain level during the polymerization. In addition, focusing on the conventional method, namely, since the synthesized PAS mostly has a low melting temperature (Tm value), the thermal stability with the applied temperature is lowered, thereby describing a method of simultaneously obtaining the improved effect

In order to find a way to improve the prior art, the present inventors have conducted extensive studies and found that PDS is very inexpensive while having an equal or higher effect of removing iodine contained in PAS polymer, and particularly that the synthesized PAS polymer has high melting temperature Tm and improved thermal stability. The present invention has been completed based on these studies. Accordingly, it is an object of the present invention to provide a process for preparing PAS, which is not only effective in reducing the production cost and iodine content of PAS polymer, but also improves the properties of PAS, such as thermal stability.

Specifically, the present invention relates to a method for preparing polyarylene sulfide, wherein the preparation is performed by polymerization of reactants including di-iodo aromatic compound and sulfur compound, wherein the method further comprises adding diphenyl disulfide as a polymerization inhibitor in an amount of 0.01 to 10.0 wt% relative to the weight of PAS to the reactants to form polyarylene sulfide having a melting temperature of 265 ℃ -.

The final polyarylene sulfide product of the present invention has a melting temperature (Tm) of 265 ℃ and 320 ℃, preferably 268 ℃ and 290 ℃, more preferably 270 ℃ and 285 ℃, thus ensuring a high melting temperature (Tm) range, and thus the polyarylene sulfide of the present invention can exert good properties such as high strength and increased thermal resistance when applied as an engineering plastic.

On the other hand, the polyarylene sulfide prepared by the preparation method according to the above-described embodiment of the present invention shows high strength characteristics, i.e., 600-800kgf/cm measured according to ASTM D638²The tensile strength of (2).

In addition, the polyarylene sulfide has an iodine content of 10 to 10,000ppm, preferably 100-4,500ppm, more preferably 150-3,000ppm, most preferably 200-1,500 ppm. In the invention, diphenyl disulfide is effectively added as a polymerization inhibitor, and the iodine content can be obviously reduced compared with the prior art, so that the risk of corrosion of processing machines can be minimized.

The polyarylene sulfide has a melt viscosity of 100-. By ensuring such enhanced melt viscosity, the polyarylene sulfide of the present invention can achieve good properties such as high strength and increased thermal resistance when applied as engineering plastics.

On the other hand, the polymerization reaction may be carried out after the reactants are melt-mixed. Thus, according to a preferred embodiment of the present invention, the reactants comprising the diiodo aromatic compound and the sulfur compound are melt mixed at 150 ℃ and 250 ℃ and then subjected to polymerization.

The polymerization reaction is not limited as long as it can be carried out. The polymerization reaction can be carried out for 1 to 30 hours under initial reaction conditions of a temperature of 180-250 ℃ and a pressure of 50to 450torr so that the final reaction conditions are changed to a temperature of 270-350 ℃ and a pressure of 0.001 to 20 torr. When polymerization is carried out under elevated temperature and reduced pressure from the initial temperature and pressure conditions to the final temperature and pressure conditions, not only the polymerization reaction rate is high, but also the properties of the polymerized polyarylene sulfide, such as thermal stability and mechanical properties, are advantageous.

The diiodo aromatic compound used in the present invention includes at least one selected from the group consisting of Diiodobenzene (DIB), diiodonaphthalene, diiodobiphenyl, diiodobisphenol and diiodobenzophenone, but is not limited thereto. These compounds may have a substituent such as an alkyl group or a sulfo group, or may be aryl compounds containing an oxygen atom, a nitrogen atom or the like. There are several isomers depending on the position of the iodine substituent. The most preferred compounds are those in which the iodine substituents are located symmetrically at the furthest distance on both ends of the molecule, such as pDIB, 2, 6-diiodonaphthalene and p, p' -diiodobiphenyl.

There is no limitation on the form of the sulfur compound used herein. Generally, sulfur is present in the form of a ring in which eight sulfur atoms are bonded (cycloocitasulfur; S8) at ordinary temperature. However, the sulfur compound may be any type of commercially available solid sulfur.

According to an embodiment of the present invention, the PAS polymerization process in the method is described in more detail as follows: the diiodo aromatic compound and sulfur as reactants are melted and mixed together with a relatively small amount of additives, a catalyst such as a nitro compound, PDS and a stabilizer are added as necessary, and polymerization is carried out at a high temperature of 180-250 deg.C, preferably 240 deg.C or higher.

More preferably, as previously described, the polymerization is carried out at initial reaction conditions, i.e., at a temperature of 180-250 ℃ and a pressure of 50-450torr, with a temperature of 270-350 ℃ and a pressure of 0.001-20 torr, varied to final reaction conditions, for 1-30 hours.

In particular, the preparation process of the present invention involves carrying out the polymerization of diiodo aromatic compounds and sulfur compounds in the presence of a nitrobenzene-based catalyst.

The present inventors have found that when a polyarylene sulfide is prepared by polymerizing a diiodo aromatic compound and a sulfur compound and polymerized using a nitrobenzene-based catalyst, a PAS product having a high melting temperature and high thermal stability is prepared. In fact, the polymerization reaction proceeds without great problems even in the absence of a catalyst. However, as shown in comparative example 1, the melting temperature at the time of PPS polymerization without a catalyst becomes low, resulting in a problem of heat resistance of the product. Therefore, it is very important to select a suitable reaction catalyst. The catalyst is 1, 3-diiodo-4-nitrobenzene or 1-iodo-4-nitrobenzene, etc., but is not limited thereto.

In addition, the method for preparing polyarylene sulfide of the present invention is characterized by using diphenyl disulfide (diphenyl disuldife) as a polymerization inhibitor.

In the present invention, the polymerization terminator is used to remove iodine molecules remaining at the ends of PAS molecules from the polymer chain. Even after the best efforts are made to remove iodine molecules in the polymer, the PAS molecules may react with a very small amount of sulfur molecules present in the polymer as long as there is residual iodine at the ends of the PAS molecules. When PAS is heated for processing herein, this small amount of iodine comes out of the polymer, causing corrosion of the processing machinery. In addition, since iodine is expensive, a polymerization inhibitor is also required from the viewpoint of recovering iodine used as much as possible. This prevents even an abnormal increase in the viscosity of the polymer during molding. In other words, it is essential to select an effective polymerization terminator in the polymerization of PAS.

The amount of the PDS used as the polymerization inhibitor is not particularly limited, and may be 0.01 to 10.0 wt.%, preferably 0.05 to 7.5 wt.%, more preferably 0.1 to 5.0 wt.% relative to the weight of polyarylene sulfide (PAS) prepared from the reaction of diiodo aromatic compound and sulfur compound. The use of the PDS in an amount less than 0.01 wt.% has little effect on the PDS, while the use of the PDS in an amount more than 10.0 wt.% causes the PAS viscosity to become low and the efficiency to deteriorate due to the excessive use of the raw material.

In addition to this, the method for synthesizing PAS from diiodoarylene and sulfur as raw materials is characterized in that disulfide (disulfide) and polysulfide (multisulfide) are contained in the synthesized polymer chain. The sulfide adversely affects the thermal stability of PAS and deteriorates resistance to oxygen and organic solvents. PDS is active against di-and polysulfides, thus improving the properties of PAS at the same time.

Therefore, the amount of disulfide bonds contained in the polyarylene sulfide of the present invention is 0.001 to 5.0%, preferably 0.01 to 3.0%, relative to the weight of sulfur.

The present invention also provides a polyarylene sulfide prepared by the above method and having a melting temperature of 265 ℃ and 320 ℃.

The present invention also provides an article prepared by molding the polyarylene sulfide, which may be provided in the form of a molded article, a film, a sheet, or a fiber.

The polyarylene sulfide of the present invention can be used by processing into any type of molded article by injection molding or extrusion molding. Examples of the molded article include an injection molded article, an extrusion molded article, or a blow molded article. For injection molding, the molding temperature is preferably 30 ℃ or higher, more preferably 60 ℃ or higher, most preferably 80 ℃ or higher in view of crystallization; it is preferably 150 ℃ or less, more preferably 140 ℃ or less, and most preferably 130 ℃ or less in view of the deformation aspect of the sample. These molded articles can be used as electric/electronic parts, building members, automobile parts, mechanical parts, daily necessities, and the like.

As the film or sheet, an unoriented film or sheet, a uniaxially oriented film or sheet, a biaxially oriented film or sheet, and the like can be prepared. As fibers, undrawn fibers, drawn fibers, super-drawn fibers, and the like can be prepared, and can be used as woven fibers, knitted fibers, nonwoven fibers (spunbond, meltblown, or woven fibers (staple)), ropes, nets, and the like.

Hereinafter, the present invention is described in further detail by way of examples and comparative examples, but the scope of the present invention is not limited thereto.

[ specific examples ] preparation of polyarylene sulfide

Example 1

0.60g of PDS (0.65% by weight relative to the weight of the final PPS product) was added to 300.00g of pDIB and 27.00g of sulfur, and the mixture was heated to 180 ℃. After completely melting and mixing, the mixture was subjected to polymerization reaction under final conditions of a temperature of 220 ℃ and a pressure of 200 Torr (Torr), followed by gradually increasing the temperature to 320 ℃ and reducing the pressure to 1 Torr (Torr) for 8 hours. 92g of polyphenylene sulfide PPS was prepared by the polymerization reaction.

The polymer product was 89.1g (yield 96.7%), had a Melt Viscosity (MV) of 5,300 poise, a melting temperature (Tm) of 274.3 ℃, an iodine content of 610ppm, and a disulfide bond content of 0.5% by weight.

Example 2

The polymerization was carried out under the same conditions as in example 1, except that 1.00g of PDS was added in an amount of 1.1% by weight relative to the weight of PPS, and the operation was carried out as described in example 1. The polymer properties were analyzed in the same manner as described in example 1. The polymer product was 90.2g (yield 98.3%), had a Melt Viscosity (MV) of 1,800 poise, a melting temperature (Tm) of 277.5 ℃, an iodine content of 250ppm, and a disulfide bond content of 0.4% by weight.

Example 3

The polymerization was carried out under the same conditions as in example 1, except that 0.3g of 1, 3-diiodo-4-nitrobenzene was added as a reaction catalyst during the first melt-mixing of pDIB and sulfur and 1.00g of PDS was added at 1.1% by weight relative to the weight of PPS, and the operation was carried out as described in example 1. The polymer properties were analyzed in the same manner as described in example 1. The polymer product was 90.9g (yield 99.0%), had a Melt Viscosity (MV) of 2,500 poise, a melting temperature (Tm) of 277.1 ℃, an iodine content of 300ppm, and a disulfide bond content of 0.3% by weight.

Comparative example preparation of polyarylene sulfide

Comparative example 1

Polymerization was carried out under the same conditions as in example 1, except that an unseparated polymerization inhibitor was added, and the operation was carried out as described in example 1. The polymer properties were analyzed in the same manner as described in example 1. The polymer product was 88.1g (yield 95.9%), Melt Viscosity (MV) 10,000 poise, melting temperature (Tm) 235.5 ℃, iodine content 7,000ppm, and disulfide bond content 3.5% by weight.

Comparative example 2

The polymerization was carried out under the same conditions as in example 1, except that 1.50g of 4-iodobiphenyl was added without using PDS, and the operation was carried out as described in example 1. The polymer properties were analyzed in the same manner as described in example 1. The polymer product was 89.5g (yield 97.5%), had a Melt Viscosity (MV) of 2,600 poise, a melting temperature (Tm) of 235.0 ℃, an iodine content of 1,500ppm, and a disulfide bond content of 3.0% by weight.

Comparative example 3

The polymerization was carried out under the same conditions as in example 1, except that 0.3g of 1, 3-diiodo-4-nitrobenzene was added as a reaction catalyst during the initial melt-mixing of pDIB and sulfur without using PDS, and the operation was carried out as described in example 1. The polymer properties were analyzed in the same manner as described in example 1. The polymer product had a Melt Viscosity (MV) of 8,750 poise, a melting temperature (Tm) of 252.7 ℃, an iodine content of 5,500ppm, and a disulfide bond content of 2.0% by weight.

Comparative example 4

The polymerization was carried out under the same conditions as in example 1, except that 10.0g of PDS was added in an amount of 10.9 wt.% relative to the weight of PPS, and the operation was carried out as described in example 1. The polymer properties were analyzed in the same manner as described in example 1. The polymer product was 92.8g (yield 101.1%), Melt Viscosity (MV) 10 poise, melting temperature (Tm) 260.8 ℃, iodine content 1,000ppm, and disulfide bond content 0.50 wt%.

[ Experimental example ] measurement of Properties of polyarylene sulfide

Properties of the polyarylene sulfide prepared according to examples 1 to 3 and comparative examples 1 to 4 were measured by the following methods and are shown in Table 1.

1. Melt viscosity measurement

Melt Viscosity (MV) was measured using a rotary disc viscometer () at 300 ℃.

2. Melting temperature measurement

The melting temperature was measured using a Differential Scanning Calorimeter (DSC).

3. Analysis of iodine content

In order to analyze the iodine content of the resins prepared in examples and comparative examples, each sample was ground, and a quantitative sample was burned and ionized in an adsorbent such as pure water. Combustion ion chromatography (combusion chromatography) for measuring the concentration of iodide ions was then used. Here, AQF-100 product of Mitsuubishi is used as a combustion system, and ICS-2500 product of DIONEX is used as an IC system.

4. Disulfide bond ratio measurement

In order to determine the disulfide bond ratio included in the resins prepared in examples and comparative examples, the theoretical amount of sulfur contained in polyarylene sulfide was subtracted from the total amount of sulfur measured by elemental analysis to obtain a weight of sulfur, which was then divided by the theoretical amount of sulfur in polyarylene sulfide and then multiplied by 2. The values thus obtained represent the values in weight% included in the polyarylene sulfideII Sulfur bond ratio. Here, the elemental analysis used the EA1110 product from CE Instruments.

5. Tensile strength

The resin was injection molded into dog bone (dog bone) shaped specimens and held under the experimental conditions (23 ℃, relative humidity RH 50%) for 48 hours, after which the tensile strength was measured according to the method specified in ASTM D638 test method of the us standard test method.

[ Table 1]

As shown in Table 1, the polyarylene sulfides according to examples 1 to 3 of the present invention can not only significantly reduce the iodine content and the disulfide bond content, but also ensure an increase in the melting temperature Tm to maintain or improve other properties, thereby being able to obtain preferable thermal stability, as compared to the polyarylene sulfides of comparative examples 1 to 4 in which no polymerization inhibitor is used, or a polymerization inhibitor is excessively used, or an iodine compound known as a conventional polymerization inhibitor is used.

Moreover, the resins of comparative examples 1 to 4 cause deterioration of thermal properties including melting temperature, and thus cannot satisfy the requirements of high strength and increase of thermal resistance when applied as engineering plastics. Specifically, the resin of comparative example 4 using an excessive amount of PDS showed a significant decrease in melt viscosity and tensile strength, and thus had a problem that a sufficiently high strength could not be obtained for use as an engineering plastic.

Claims (7)

1. A method for preparing a polyarylene sulfide, wherein the polyarylene sulfide is prepared by polymerization of reactants including a diiodo aromatic compound and a sulfur compound, the method comprising:

0.01 to 10.0 wt% of diphenyl disulfide, relative to the weight of the polyarylene sulfide, is further added to the reactants to form a polyarylene sulfide having a melting point of 265-320 ℃.

2. The method for preparing polyarylene sulfide according to claim 1, wherein the polymerization is carried out under initial reaction conditions including a temperature of 180-250 ℃ and a pressure of 50-450torr for a temperature rise and a pressure drop such that final reaction conditions are changed to a temperature of 270-350 ℃ and a pressure of 0.001-20 torr for 1-30 hours.

3. The method for preparing polyarylene sulfide according to claim 1, wherein the polyarylene sulfide has an iodine content of 10 to 10,000 ppm.

4. The method for preparing polyarylene sulfide according to claim 1, wherein the polyarylene sulfide has a melt viscosity of 100-.

5. The method for preparing polyarylene sulfide according to claim 1, wherein the polymerization reaction is performed in the presence of a nitrobenzene-based catalyst.

6. The method for preparing polyarylene sulfide of claim 1, wherein the diiodo aromatic compound includes at least one selected from the group consisting of diiodobenzene, diiodonaphthalene, diiodobiphenyl, diiodobisphenol and diiodobenzophenone.

7. The method for preparing polyarylene sulfide according to claim 1, wherein the polyarylene sulfide includes 0.001 to 5.0 wt% of disulfide bond with respect to the total weight of sulfur.