JPH02298527A - Cellular sintered body composed of polyarylene sulfide - Google Patents

Abstract

PURPOSE:To obtain a cellular sintered body, having preferred voids and excellent in dimensional stability, heat, chemical resistance, etc., with a low molding shrinkage factor by heat-treating powder of a polyarylene sulfide under specific temperature conditions, then heating and sintering the resultant heat-treated powder. CONSTITUTION:A cellular sintered body obtained by heat-treating (A) powder of a substantially linear polyarylene sulfide having 500 to 5X10<4>P, preferably 10<3> to 10<4>P melt viscosity (at 310 deg.C and 1200/sec shearing rate), preferably a block copolymer, etc., composed of 50-95mol% recurring units expressed by formula I and 5-50mol% blocks expressed by formula II at a temperature above the melting crystallization temperature and below the melting point for 0.5-600min and having 2X10<3> to 10<5>P, preferably 3X10<3> to 7X10<4>P, heating and sintering the resultant heat-treated powder (B) at a temperature above the softening temperature and below the decomposition temperature and preferably further heat-setting the sintered body at a temperature below the melting point.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to polyarylene sulfide (hereinafter referred to as rPAS).
Regarding porous sintered bodies (abbreviated as J), more specifically, porous sintered bodies with low molding shrinkage, suitable porosity, and excellent dimensional stability, heat resistance, chemical resistance, mechanical properties, etc. Regarding sintered bodies.

[Prior Art] Conventionally, porous sintered bodies made of resins such as polyethylene, polypropylene, polyvinyl chloride, polyamide, polymethyl methacrylate-1, cellulose resin, and polyvinylidene fluoride have been used as porous polymer materials. It has been mass-produced and is used in a wide range of fields such as sewage, frozen plains, livestock farming, various industrial wastewater treatment, and domestic wastewater treatment.

However, in recent years, due to stricter pollution prevention regulations in the chemical industry and demands for more complete disinfection and sterilization in the medical field, the requirements for porous sintered bodies used in these fields have become more sophisticated. Things and 1 (are coming. In other words,
Heat resistance and chemical resistance higher than conventional ones are required, for example, 10
There is a strong demand for a sintered body that can withstand repeated disinfection and sterilization using dry heat or warm heat at temperatures above 0''C, as well as long-term contact with chemicals such as acids, alkalis, hydrochloric acid, oils, and organic solvents at high temperatures.

A specific example of a field that requires heat resistance is, for example, porous sintered polymers for waste gas filters in incinerators, which require heat resistance of 120°C or higher to be suitable for that purpose. shall be. However, polyamide-based porous sintered bodies currently on the market for exhaust gas filters have insufficient heat resistance and are unsuitable for use at temperatures above 120"C.

On the other hand, as a porous sintered body having heat resistance, a porous sintered body made of aromatic polysulfone (JP-A-52-1/
I, No. 6468) and porous sintered bodies made of polyamideimide (Japanese Patent Application Laid-Open No. 57-874.36), but in both cases, pellets are mechanically crushed to prepare the material for sintering. However, the means to obtain the powder are not efficient (and the raw materials are expensive).
Industrialization is difficult to achieve.

In recent years, PAS, represented by polyphenylene sulfide, has been developed as an engineering brass with excellent heat resistance and chemical resistance.
Since the particle size can be controlled during polymerization, it has the advantage that it can be used as a powder for sintering without going through a pulverization process. However, PAS particles obtained by polymerization generally have a large number of fine pores, a large specific surface area (and a small bulk density), so they can be used to create pores using a normal sintering method. When molding a high-quality sintered body, there are problems such as a large molding shrinkage rate and a sintered body with poor dimensional stability.In addition, among PPS,
If the molecular weight is increased by curing due to oxidative crosslinking, the PPS particles lack binding properties, and individual powders tend to fall apart even after sintering (sintering with excellent mechanical strength) Can't get the body.

As described above, the reality is that a porous sintered body that has properties such as dimensional stability, heat resistance, chemical resistance, and mechanical properties and can be industrialized has not yet been developed.

[Problems to be Solved by the Invention] The purpose of the present invention is to overcome the above-mentioned problems of the prior art, and
The object of the present invention is to provide a porous sintered body having a small mold shrinkage rate, a suitable porosity, and excellent dimensional stability, heat resistance, chemical resistance, mechanical properties, etc.

The present inventors, in order to overcome the problems of the prior art,
As a result of extensive research, we found that the substantially linear PAS material obtained by polymerization can be used as it is for sintering.
discovered that a porous sintered body having excellent physical properties that overcomes the above drawbacks can be obtained by performing heat treatment under specific conditions before sintering, and based on that knowledge, completed the present invention. reached.

[Means for Solving the Problems] Thus, according to the present invention, the melt viscosity η* (310°C
1) measured at a shear rate of 1200/sec) is 500 to 5 x 104
Poise's substantially linear polyarylene sulfide powder is heat-treated at a temperature above the melt crystallization temperature of the polyarylene sulfide and below the melting point for 0.5 to 600 minutes, and then the powder is A porous sintered body obtained by heating and sintering polyarylene sulfide at a temperature above the softening temperature and below the decomposition temperature is provided.

The present invention will be explained in detail below.

(PAS) PAS used as a raw material for the porous sintered body of the present invention has a melt viscosity η* of 500 to 5X 10' poise, preferably 103
~104 poise, particularly preferably 2X103 to 8X10
3 poise substantially linear polymer.

Polymers with a low melt viscosity of PAS with a melt viscosity η* of less than 500 poise cannot be sintered even after heat treatment, or result in a mechanically fragile sintered body; conversely, polymers with a high viscosity exceeding 5 x 104 poise Polymers of 1 to 1 are undesirable because the melt adhesion of the PAS particles deteriorates, resulting in a mechanically fragile sintered body.

Such PAS is produced by combining an alkali metal sulfide and a dihaloaromatic compound in an organic amide solvent such as N-methylpyrrolidone in the presence of water, as described in JP-A-61-7332. In addition, it can be suitably obtained in the form of particles (as a powder) by a specific two-step temperature-rise polymerization method.

The PAS used in the present invention is preferably a substantially linear PAS containing polyphenylene sulfide, particularly preferably 70% by weight or more, more preferably 90% by weight or more of p-phenylene sulfide as a repeating unit of the polymer. Homopolymers or copolymers of poly-p-phenylene sulfide are preferred.

Corresponding to the 50% by weight or more of p-phenylene sulfide units, the PAS may also contain less than 50% by weight of other copolymerizable repeating units. An example of such a repeating unit is:

In addition, in the present invention, as PAS, a block copolymer consisting of repeating units or a PAS containing the block copolymer is used.
AS compositions can be used.

The PAS used in the present invention is a substantially linear polymer powder having the shape of particles obtained by polymerization.

Here, the term "substantially linear" refers to a polymer obtained from monomers mainly consisting of difunctional monomers, rather than a polymer obtained by thickening (curing) through oxidative crosslinking.However, By copolymerizing polyhelobenzene such as trichlorobenzene as a minor component,
PA with some crosslinked structure and/or branched structure introduced
S can also be suitably used as long as it does not impair the present invention.

Various fillers, additives, etc. can be appropriately blended into this PAS as necessary.

(Heat treatment) In the present invention, particulate PAS obtained by polymerization
The main feature is that before sintering the powder, heat treatment is performed under specific conditions.

In the heat treatment, the particulate PAS powder obtained by polymerization is
0.5 to 0.5 at a temperature above the melting crystallization temperature of PAS and below the melting point
This is carried out by heating for about 600 minutes, preferably about 1 to 300 minutes.

If the heat treatment temperature is lower than the melt crystallization temperature of PAS, the heat treatment effect will be small, the density of the particles will not increase, shrinkage will occur during molding of the porous sintered body, and it will be difficult to obtain a porous sintered body with good dimensional accuracy. Furthermore, if the heat treatment temperature is higher than the melting point of PAS, sintering will occur during the heat treatment, making it difficult to return to the original powder state.

The heat treatment time is about 0.5 to 600 minutes, preferably about 1 to 300 minutes, from the time when the heat treatment temperature reaches a temperature higher than the melt crystallization temperature and lower than the melting point of PAS.

If the treatment time is too short, the molding shrinkage rate will be large and dimensional stability will be lacking, while if the treatment time is too long, thermal crosslinking or oxidative crosslinking reactions will proceed too much and the sinterability of the particles will deteriorate.

The heat treatment may be carried out in air (or by replacing a portion of the air with an inert gas such as nitrogen gas), but is not particularly limited.

The melt viscosity η* (measured at 310° C. and shear rate of 1200/sec) of PAS after heat treatment is 2×10 3 to 10 5 poise, preferably 3×1. O”~7×104 poise,
Particularly preferably, it is 5 x 10" to 5 x 10' voice. If the melt viscosity η* after heat treatment is too low, less than 2 There are problems such as cracking, and if it exceeds 105 poise, the melt adhesion of the RAS particles deteriorates, resulting in a mechanically fragile sintered body. In particular, by setting the melt viscosity η* after heat treatment to 5 x 103 to 5 x 10'voice, the sintering temperature can be increased, resulting in a sintered body with good pore shape and excellent mechanical properties. can get.

Although the heat-treated PAS powder has particles that are sintered together, it can be easily returned to its original powder state by pulverizing it with a mixer or the like.

When heat-treated PAS particles are sintered, a porous sintered body with a smaller thermal shrinkage rate and better dimensional stability can be obtained than when untreated PAS particles are used. The reason for this is that when RAS particles obtained by polymerization are heat-treated, the amorphous portion of the particles melts and the fine pores become clogged, resulting in an increase in the bulk density of the particles (and a decrease in melt viscosity due to thermal crosslinking, etc. Heat-treated PAS particles are thickened by crosslinking, so even when sintered at a temperature considerably higher than the particle's melting temperature, the particles do not cause large melt flow and have low bending flexibility. A porous sintered body with a large pore size can be obtained.Furthermore, since the shape of the particles does not collapse, a sintered body with a constant pore shape can be obtained.

(Sintering method) The sintering method is not particularly limited, and for example, after filling the heat-treated PAS powder into a mold while slightly vibrating, at a temperature higher than the softening temperature and lower than the decomposition temperature of the PAS, Commonly used methods such as heating for a certain period of time in air or an inert gas atmosphere can be employed. Here, the softening temperature can be determined by a load deflection temperature test method, and the decomposition temperature can be determined by a thermogravimetry method.

The sintering temperature of PAS powder is usually about 270 to 450°C, and the sintering time is about 05 to 600 minutes. If the sintering temperature is lower than 270''C, the sinterability will be weak, and even if heated for a long time, oxidative crosslinking and thermal crosslinking reactions will proceed, so the sinterability will not improve.

Moreover, if the temperature is raised to more than 450°C, PAS decomposes, which is undesirable.

Also, after sintering, the temperature below the melting point of PAS, preferably 1
Heat setting at 50 to 250'C for about 5 to 600 minutes is preferable because the crystallinity of the sintered body becomes high and the heat resistance improves.

The average particle size of the PAS particles used is not particularly limited, but is usually used in the range of 5 μm to 3 mm, particularly 20 μm to 3 mm.
A shape close to a sphere in the range of μm to 1,000 μm is preferable.

The apparent porosity of the obtained sintered body is 10% to 80%.
% is desirable; if it is less than 10%, air permeability and water permeability will not be sufficient, and if it is more than 80%, the strength will be low.

(Applications) The porous sintered body of the present invention has properties such as heat resistance and chemical resistance that RAS has, and as a sintered body, it has low molding shrinkage, suitable porosity, and dimensional stability. Because of its excellent heat resistance and mechanical properties, it can be used in a wide range of fields, including incinerator waste gas filters, acid solution filters, and high-temperature solvent filters.

[Examples] The present invention will be described below with reference to Examples and Experimental Examples, but the present invention is not limited to these Examples.

[Synthesis Experiment Example 1] (Synthesis of poly-p-phenylene sulfide) In a titanium-lined polymerization can, 90 kg of N-methylpyrrolidone (hereinafter abbreviated as rNMPJ) and hydrous sodium sulfide (water content 54% by weight) were placed in a titanium-lined polymerization can.
3.0 kg and gradually 20 kg under nitrogen gas atmosphere.
While increasing the temperature to 3°C, a mixture of water and NMP 13.7
kg (including 8.3 kg of NMP) and 6.2 mol of H2S were distilled off.

Next, 28.8 kg of p-dichlorobenzene (hereinafter abbreviated as rPDCB) and 15 kg of NMP were added, and 21
Polymerization was carried out at 0°C for 10 hours. Water 9.32 in this system
After adding 1.0 kg by pressure, polymerization was further carried out at 260° C. for 10 hours. After cooling, the reaction solution was sieved through a screen with an opening of 1 mm to separate the poly-p-phenylene sulfide granular polymer, which was then washed with acetone and water to obtain a washed polymer (polymer p).

Next, it was immersed in a 2% ammonium chloride aqueous solution and treated at 40°C for 30 minutes, washed with water, and then dried. The average particle size of the particles was 400 μm. The resulting polymer had a melt viscosity of 257° poise (310°C, shear rate 1200/sec), a melting point of 305°C, and a melt crystallization temperature of 188°C. The melting point is determined by weighing about 1 omg of the particulate polymer powder obtained by polymerization and heating it at a rate of 10°C/min from room temperature in an inert gas atmosphere using a differential scanning calorimeter (DSC). and measured. On the other hand, the melt crystallization temperature was determined by weighing 10 mg of polymer powder, then heating it from room temperature to 340°C at a rate of 10,307 minutes in an inert gas atmosphere using DSC, holding it at 340°C for 3 minutes, and then The temperature was lowered at a rate of °C/min, and the temperature at the peak of crystallization was measured.

[Synthesis Experiment Example 2] (Synthesis of poly-p-phenylene sulfide) 1.0 kg of NMPI and Na2S"5HtO were placed in a titanium-lined polymerization can.
20.0 mol and gradually added 2 in a nitrogen gas atmosphere.
1.27 kg of water, NMP 1.5 while increasing the temperature to 00℃
7 kg and 0.46 mol of H2S were distilled off. 13
After cooling to 0°C, 19.73 mol of PDCB and NMP
3.2 kg was added and polymerization was carried out at 210'C for 9 hours. Next, water was added to the polymerization system so that the coexisting water in the polymerization system had a molar ratio of H20/Na2S of 4.0, and the temperature was raised to 265° C. under a nitrogen gas atmosphere, and polymerization was further carried out for 6 hours. After cooling, the reaction solution was filtered, washed with water, and dried to obtain a granular polymer (polymer P2). The average particle size of the obtained polymer was 450 μm. Also, the melt viscosity is 690
0 poise (310°C, shear rate 1200/sec), melting point was 307°C, melt crystallization temperature was 186°C.

[Synthesis Experiment Example 3] (Synthesis of phenylene sulfide block copolymer) NMPIl, Okg and Na2S in a titanium-lined polymerization can
・0 mol of 5H-016 was charged, and the temperature was gradually raised to 200° C. under a nitrogen gas atmosphere to distill out moisture. H
, S was 1.5 mol%. After cooling PDCB1G, 1Mo, 11. and 3.0 kg of NMP were charged, and polymerization was carried out at 210'C for 10 hours. Then, 53 mol of water was added to this system and the temperature was reduced to 0.25 mol at 250 °C.
A reaction mixture (P) was prepared by reacting for a period of time, and after cooling, it was taken out from the polymerization vessel.

(P) Sampling a small amount of liquid and measuring the degree of polymerization of the produced p-phenylene sulfide prepolymer (fluorescent X-ray method)
did. The degree of polymerization was 300.

Separately, NMPIl, Okg and 16.0 mol of Na2S ・5H* 0 were charged into a titanium-lined polymerization can, and about 2
The temperature was raised to 00°C to distill water (S loss amount = 1
．． 5 mol%). Then m-dichlorobenzene15.
5 mol, NMP3. Okg and 53 moles of water were added to prepare an unreacted mixed liquid (M), and after cooling, it was taken out from the polymerization vessel.

Next, 13.6 kg of liquid (P) and 3.4 kg of liquid (M) were charged into a titanium-lined polymerization can, and reacted at 262°C for 5 hours. After the reaction was completed, the reaction mixture was filtered, washed with hot water, and dried under reduced pressure to obtain a phenylene sulfide block copolymer (polymer P3).

According to infrared analysis, the repeating single LLm belonging to the block has a melt viscosity of 3250 poise (310°C1 shear rate 1
200/sec).

Further, the melting point was 288°C, and the melt crystallization temperature was 186°C.

[Example 1] 500 g of 21 particles of the polymer of Synthesis Experimental Example 1 (powder with an average particle size of 150 μm) bathed in a 60-mesh screen
was placed in a hot air circulation dryer and heating was started.

When the temperature of the powder reached 298°C, it was maintained at this temperature for 30 minutes, then the heater was turned off and the circulation fan continued to operate to cool the powder until the temperature of the powder reached 100°C.
It was removed from the dryer when the temperature was below ℃. Since each particle was in a lightly sintered state, it was placed in a mixer and pulverized to return it to its original powder form.

Table 1 shows the melting point, melt crystallization temperature, and melt viscosity of the polymer as the properties of the powder after heat treatment. (shown below).

The heat-treated powder described above was filled into a stainless steel mold with inner frame dimensions of 15 cm wide, 15 cm high, and 0.3 cm thick so as to be as dense as possible while pie-breaking. . The mold was set in a hot air circulation dryer, the temperature in the dryer was set at 335°C, and the mold was heated to perform sintering. When the temperature of the powder reaches 330℃, the heater is turned off and the circulation fan continues to operate to allow natural cooling, and the temperature of the sintered body reaches 1.
I took it out when the temperature dropped below 00'C.

This sintered body was annealed (heat-set) at 204°C for 4 hours. Table 1 shows the bulk densities before and after sintering (filling density before sintering and sintered body density after sintering) and the rate of change thereof. The packing density was determined from the apparent volume and weight when the heat-treated powder was densely packed into the filling container, and the sintered body density was determined from the apparent volume and weight of the sample. On the other hand, the rate of change in density was determined using the following formula.

[(Sintered compact density - Packing density) / Packing density) x 100 From the sintered compact density (g/cc) and the true specific gravity of poly p-phenylene sulfide (1.36, crystallinity 40%), the following formula is calculated. The apparent porosity was determined to be 42.0%.

[1-(Sintered compact density/true specific gravity) The bending test of the IX100 sintered compact was performed using a sintered compact specimen cut to a length of 127 mm and a width of 12°7 mm, with a span distance of 80 mm in accordance with ASTM D-790-63. , and the bending load rate was 2.0 mm/min. Note that the maximum amount of deflection was measured. The results are shown in Table 1.

[Example 2] 500 g of 22 particles of the polymer of Synthesis Experimental Example 2 (powder with an average particle size of 150 μm) bathed in a 60-mesh screen
As in Example 1, heat treatment was performed by holding the powder temperature at 295° C. for 30 minutes.

A sintered body was formed using the powder after this heat treatment. The temperature conditions at that time were a controlled temperature of 335°C in the dryer.
When the powder temperature reached 330°C, the heater was turned off, the powder was allowed to cool naturally, and the sintered body was taken out. The properties of the powder after heat treatment, the bulk density and rate of change, and the physical properties of the sintered body are shown in Table 1. ).

[Example 3] 500 g of the polymer P of Synthesis Experiment Example 3 (powder with an average particle size of 150 μm) bathed in a 60-mesh screen,
Heat treatment was performed by maintaining the powder temperature at 280° C. for 30 minutes.

A sintered body was formed using this powder. The temperature conditions are
The temperature inside the dryer was controlled at 310°C, and when the powder temperature reached 305°C, the heater was turned off, the powder was allowed to cool naturally, and the sintered body was taken out. Table 1 shows the properties of the powder after heat treatment, the bulk density and rate of change, and the physical properties of the sintered body.

[Comparative Example 1] Polymer P used in Example 1 (a 60-mesh screen product) was set in a hot air circulation dryer without being heat-treated. The set temperature was controlled at 310'C, and when the temperature of the powder reached 305°C, the heater was turned off and a sintered body was obtained by natural cooling. Table 1 shows the properties of the powder, bulk density and change rate, and physical properties of the sintered body.

[Comparative Example 2] Polymer P2 (60 mesh scrim bath product) used in Example 2 was sintered in the same manner as Comparative Example 1 without heat treatment. However, the temperature setting of the hot air circulation dryer is 3.
The temperature was set at 12°C, and when the powder temperature reached 307°C, heater heating was stopped and the powder was allowed to cool naturally. Table 1 shows the measurement results of the physical properties of the obtained sintered body.

[Comparative Example 3] Powder of polyphenylene sulfide (trade name: Rydon P-4) manufactured by Phillips Vetroleum was sintered in the same manner as in Comparative Example 1 without heat treatment. However, the set temperature of the hot air circulation dryer was 290°C, and when the temperature of the sintered body reached 285°C, the heater heating was stopped and the sintered body was allowed to cool naturally. Small cracks were formed throughout the sintered body due to shrinkage, and a good sintered body could not be obtained. The measurement results of physical properties are shown in Table 1.

As is clear from Table 1, the present invention (Examples 1 to 3) has a small density change rate before and after sintering, has a small molding shrinkage rate, has excellent dimensional stability, and has excellent bending strength, deflection, etc. It can be seen that the mechanical properties and porosity are also excellent. On the other hand, those without heat treatment (Comparative Examples 1 and 2) and those using cured polyphenylene sulfide (Comparative Example 3) cannot achieve the desired performance.

[Example 4] In order to evaluate the porosity of the sintered body, air was blown onto the sintered body and the flow velocity and pressure loss on the filtration surface were measured.

That is, a cylindrical mold was filled with a pie-break powder heat-treated under the conditions of Example 1 while being vibrated.

Set it in a molded hot air circulation dryer, set the temperature inside the dryer at 340°C, and when the temperature of the powder reaches 330°C, turn off the heater, allow it to cool naturally, and reduce the temperature of the sintered body to 1°C.
It was taken out when the temperature dropped to below 00°C.

This sintered body was annealed (heat-set) at 204° C. for 4 hours.

The inner diameter thus obtained was 88 mm, and the outer diameter was 109 mm.
A cylindrical sintered body with a wall thickness of 10.5 mm and a height of 149 mm was set in a pressure loss measuring device, and air was blown with an air blower to measure the flow velocity and pressure loss on the filtration surface. The results were as follows.

Table 2 The results show that the sintered body is porous and has excellent air permeability.

[Example 5] The apparent porosity and mechanical properties of the sintered body obtained in Example 1 were measured after aging at 150°C for 7 consecutive days. The results are as follows.

Table 3 The results show that the sintered body of the present invention shows little change in physical properties before and after aging and has excellent heat resistance.

〔Effect of the invention〕

The present invention provides a porous sintered body made of polyarylene sulfide, which has a small molding shrinkage rate, a suitable porosity, and has excellent dimensional stability, heat resistance, chemical resistance, mechanical properties, etc. A high quality sintered body can be provided. In the present invention, since RAS particles obtained by polymerization can be used as powder for sintering, a porous sintered body can be efficiently obtained without the need for a pulverization step.

Claims (5)

[Claims] (1) Substantially linear polyarylene sulfide powder having a melt viscosity η* (measured at 310°C and a shear rate of 1200/sec) of 500 to 5 x 10^4 poise is converted into molten crystals of the polyarylene sulfide. 0 at temperatures above the melting point and below the melting point
．． A porous sintered body obtained by heat-treating for 5 to 600 minutes and then heating and sintering the powder at a temperature above the softening temperature and below the decomposition temperature of polyarylene sulfide. (2) The porous sinter according to claim 1, wherein the polyarylene sulfide powder after heat treatment has a melt viscosity η* (measured at 310° C. and a shear rate of 1200/sec) of 2×10^3 to 10^5 poise. body. (3) After heating and sintering, the polyarylene sulfide is heat-set at a temperature below the melting point of the polyarylene sulfide.
The porous sintered body described in . (4) The porous sintered body according to any one of claims 1 to 3, wherein the polyarylene sulfide is a substantially linear polyphenylene sulfide. (5) Polyarylene sulfide has 50 to 95 mol% block of repeating unit ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and block 5 of repeating unit ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
Claim 1 containing a block copolymer consisting of ~50 mol%
Porous sintered body according to any one of items 3 to 3.