JPH03213503A - Cleaning of spinneret - Google Patents

Abstract

PURPOSE: To clean a spinneret so that the orifice of a spinneret plate is not clogged by placing the spinneret in an oxidative fused salt bath in a specific state. CONSTITUTION: A spinneret is placed in an oxidative fused salt bath at 260-482 deg.C in such a manner that its orifice lays at an angle of 30-75 deg. against the horizontal line with the end of the inlet of the orifice facing upward to make the attached matter react with the oxidative fused salt. The gas trapped inside the orifice is released from the end of the inlet of the orifice and the reaction of the attached matter with the fused salt proceeds better. The spinneret after cleaning is taken out from the fused salt and quenched.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for cleaning and removing organic substances from an orifice of a workpiece, and in particular, the present invention relates to a method for cleaning and removing organic substances from an orifice of a workpiece. The present invention relates to a method for cleaning organic polymers in close contact with the orifices of a spinneret plate used for extrusion.

[Conventional technology]

When extruding polymers into filaments through a spinneret, over time the polymers adhere to and accumulate on the orifice and surrounding surfaces.

- Once accumulation becomes significant, it becomes necessary to remove the spinneret from use and clean and remove the constituents. Since polymers usually contain fillers, such as titanium dioxide to increase opacity, the removal process must face the problem of removing these fillers as well as removing the base polymer.

The orifice is usually quite small [in some cases as small as 0.076 mm (0,003″) in diameter];
The cleaning process is also somewhat complicated by the fact that the polymers react and become tightly adhered to the surfaces of conventionally used stainless steel or other heat and corrosion resistant alloy spinnerets.

Furthermore, the large number of small holes in the spinneret are not usually formed by simple drilling (or holes formed by counterbore and/or chamfering, and spinnerets containing more than 1,000 holes). is normal.

High temperature at one end, i.e. approximately 549°C (1000°F)
Although higher temperatures are effective to liberate and decompose the attached polymer, such temperatures are usually lowered to avoid damaging the spinneret, as well as to avoid undesirable changes in the microstructure of the alloy. Must be avoided.

Furthermore, due to the small size of the orifice, purely mechanical treatments typically do not effectively reach the surfaces within the orifice.

[Problem to be solved by the invention]

Prior art cleaning methods have included ashing, chemical methods, high temperature salt baths, high pressure fluid energy, ultrasound, and combinations thereof.

All prior art methods have been unsatisfactory in at least one respect. Although the ashing method is effective in destroying the polymer, residue remains in the extrusion hole and is very difficult to remove even by high pressure fluid methods.

Furthermore, increasing the temperature in the presence of an oxidizing medium will attack the metal used to make the spinneret plate (usually some type of stainless steel).

The use of molten salts in the prior art includes the use of temperatures of about 482°C (900°F) to obtain adequate chemical activity. The salt is an oxidizing salt that helps break down the polymer, but the initial cleaning action is simply ashing.

This action is characterized by the generation of large amounts of smoke and flames on the surface of the salt bath where the polymer burns.

This large amount of smoke generation requires extensive smoke collection and treatment equipment before the exhaust gas is released to the atmosphere.

Another consideration is the rate of oxidation of the polymer at the fine tip of the spinneret, such that the locally generated temperature can be much higher than the operating temperature of the salt bath.

The high temperatures generated by the combustion of the polymer can damage the metal associated with the thinning of the sharp edges of the extrusion hole.

Metallurgical damage that occurs at the tip of the spinneret hole can result in thermal softening or twisting of sharp edges, and/or chemical degradation due to metal oxidation or intergranular erosion.

SUMMARY OF THE INVENTION The present invention is particularly applicable to cleaning organic polymers from the surface of orifices of spinneret plates used in the extrusion of polymeric fibers such as nylon, dacron or orlon. be done.

However, the present invention is useful for any cleaning when deposited organic coatings must be removed from the orifice surfaces of various metal workpieces, especially when the orifice is small and/or has a large length-to-diameter ratio. also applies.

Thus, the term spinneret or spinneret plate is intended to include any workpiece part that has orifices that have organic matter deposited thereon and from which the organic matter must be removed.

However, the present invention will describe a preferred embodiment used to clean spinnerets used to extrude organic polymeric fibers.

Briefly, the method involves immersing a spinneret plate into a bath of molten oxidized salt at a relatively low temperature to allow the salt to react with the oxide-deposited organic material.

The selection of specific molten salts is variable. however,
The salt must be oxidizing to the organic material that is just being removed, must be such that it displaces the carbon rather than carbonizing it, and must be at the temperature of use [e.g.
It must be liquid and sufficiently flowable at temperatures between 500°F and 400°F, and not react adversely with the filler or spinneret and create hazardous reaction conditions within the bath.

Particularly useful salt types are alkali metal hydroxides, preferably with alkali metal nitrates.

1 A particularly useful bath that has been successfully used is a commercially available potassium hydroxide-sodium nitrate salt bath (hereinafter referred to as nitrate-based molten salt bath A or first salt bath) available from Colleen Corporation of Detroit, Michigan. It is manufactured and sold by Kolene Corporation in the United States. This salt is about 5
8.8% potassium hydroxide, approximately 40.3% nitric acid l-
an organic compound having a melting point of about 196°C (385°F) and a low viscosity at 260°C (500°F) and above, having a composition of about 0.9% potassium permanganate as a catalyst Reacts strongly with polymers.

The reaction during organic destruction is clearly C(organic 1+2NO3→-CO2+2NO2-,
The reaction during the idle period is NO
□－＋! /! io□(Air)-NO3-0 For best results, the plate should be positioned so that the axis of the orifice extends at an angle between 30° and 75° to the horizontal.

The orifice usually has an enlarged inlet end and has a 2 These artificial ends are directed upwards.

The angular positioning of the axis and the orientation of the inlet end ensure that the gases emanating from the orifice can pass freely and that hard particles do not settle in the orifice and block the passage of salt. It is necessary to do so.

-H-wise, angles between 30° and 75° with respect to the horizontal are preferred, with angles between 45° and 60° giving best results. Also, for best results, the parts should be agitated or vibrated while in transit. This reduces the tendency for the generated gas to stick to the orifice walls.

A commercially available vibrator is used, such as a pipe roller vibrator sold by Martin Engineering, Nebonset, Illinois.

Soaking times can vary, but are typically about 15 minutes to 1 hour.

Processing is approximately 260°C to 371°G (500°F to 7
00°F) and 260°C (500°F) is just above the pour point of most polymers.

This softens the polymer and makes the reaction rate relatively slow, thus minimizing local heating and minimizing burnt residue.

A pickling bath containing equal amounts of citric acid and thorium gluconate (hereinafter referred to as organic pickling solution C) is used for washing (rinsing) in an organic acid pickling bath such as KGC manufactured by Kolin Corporation in the United States.
The liquor is maintained at 66°C (150°F) with about 5% tartaric acid to help brighten the spinneret and aid in residue removal.

The spinneret plate is removed from the salt bath, preferably cooled in hot water, and subjected to a high pressure water jet or vibratory polishing process. In some cases, this step removes most if not all of the deposited material. In that case, repeat the whole process.

The quenching and acid treatment expose new surfaces of unreacted polymers still attached to the walls, so that a second immersion in the salt bath causes further reaction.

Once the reaction is complete, the spinneret is removed, cooled and acid treated.

If the polymeric material is particularly sticky and/or the orifice is particularly small, it may be desirable to increase the temperature of the second dip process somewhat.

For example, the first salt bath treatment is at approximately 260°C (500°F).
The second time, the temperature should be up to 399°G [750°F] or slightly higher, but not above about 482°C (900°F). However, when the temperature is increased the time is somewhat shorter, generally because there is not much organic material remaining after the first soak. It is also manufactured by Colleen Corporation of Detroit, Michigan, and has a composition of about 15% sodium nitrate, 10% sodium chloride, 12% potassium hydroxide, and the balance sodium hydroxide (nitrate type). Molten salt bath agent B
It is also desirable to use a stronger salt with different ingredients from the first salt bath agent A, such as DGS manufactured by Corin Co., USA. .

In extreme cases, the process sequence may have to be repeated up to three times until the organic material is completely removed.

5 All of the various stages may be desirable in some cases, but the key stages are the melting until evidence of a reaction, e.g. the formation of gas bubbles or the apparent appearance of polymeric particles at the surface, begins to melt until it eventually stops. Immersion in an oxidizing salt bath followed by rapid cooling.

Also, the angle and orientation are important to allow trapped gas to escape but to avoid depositing particles in the orifice.

〔Example〕

EXAMPLES ■ Listed below are some typical examples of processes for removing organic residue from a spinneret.

Sample description: Two spinnerets with solidified polymer residues.

(1) Using nitrate salt bath agent A (Colleen number 6) at 343°C (650°F)...
...30 minutes (2) Post-cooling in air...
・・・・・・・・・・・・・・・・・・・・・・・・・・・・
・15 minutes (3) Cool quickly in warm water and soak as is...
・・・・・・15 minutes (4) Rinse with fresh water and air dry.

Result: 90% of macromolecules removed, some residues 6 There is a small amount of residue at the bottom of the hole.

The spinneret was recycled from steps (1) to (4) above. The polymer was completely removed.

One out of two spinnerets treated as outlined above were polished with organic pickling solution C, Colleen rKGcJ organic acid: (1) 5% organic pickling solution C (rK G CJ) to 60℃
Then, rinse for 5 minutes (2) with fresh water and air dry.

Observations: Very little smoke was generated during cleaning of these components. The reaction "peaked" when the surface of the molten salt was "covered" by a suitable amount of partially digested polymer at a time of 10 minutes.

It was during this aspect of the cleaning that a small amount of smoke was seen.

As the polymer continued to be digested by the bath and the "cover" decreased, the smoke production ceased.

The remainder of the wash cycle was unremarkable, but sporadic slow gas evolution was observed as the salt scavenged polymeric residue from deep in the counterbore or capillary.

Example II Sample Description: Weight of one spinneret with solidified nylon 66 deposit before cleaning: 4360g+ns Weight after cleaning: 4283gm5 removed weight:
The 77gm5 wash cycle consisted of: Nitrate-based molten salt bath A (Colleen number 6) at 302°C.
(575°F) ・・・・・・・・・・・・
・Post-cooling in still air for 30 minutes・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・5 minutes [temperature of parts = 216℃ (4206F)] Rinse with warm water [71℃ (1
60°Fl] .....5 minutes The inspection of the part showed that only about 50% of the spinneret holes were open.

The parts were rinsed with fresh air and the passages were dried with compressed air. Processing continued as follows for the same part: Nitrate-based molten salt bath A (Colleen number 6), 329°C.
(625'F l ・ ・ ・ ・ ・ ・I
Post-cooling with still air for O minutes... River...
・・・・・・・・・・・・Quick cooling with water at weather temperature for 5 minutes・
・・・・・・－・・・・・・・・・・・・・・・・・・
・Rinse with warm water for 1 minute (71℃ (160℃))・
......5 minutes The spinneret was thoroughly cleaned after this treatment.

Example II+ 1 spinneret, nitrate-based molten salt bath A, 357°F 675°F). ...River...Post-cooling in still air for 45 minutes...
・・・・・・・・・・・・Quick cooling with water at ambient temperature for 5 minutes・
···················eye·····
Rinse with warm water for 1 minute.
・・・・・・・・・・・・Old・・・・・・The results of the 5-minute test show that most of the passages were cleaned except for the three passages that seemed to be clogged with residue.

Example IV One spinneret with a "tough" polyester residue was used. The spinneret was not scraped of any excess residue before testing.

(1) Nitrate-based molten salt bath AC Colleen number 6) 34
3℃ (650°F) ・・・・・・・・・・・・
...15 minutes 9 (2) Rapid cooling directly with water at ambient temperature...
・・・・・・2 minutes (3) Organic pickling solution C (Colleen rK
GCJ) Organic acid 66℃f150℃)・・・・・・
...5 minutes (4) Rinse with fresh water and force dry...
...As a result, the spinneret had a shiny metallic appearance.

The inspection results showed that there was still residue in about 20 holes.

Some of this residue had the appearance of unreacted polymer, and other residue had a dark color and a "carbonaceous" appearance.

(5) Nitrate-based molten salt bath A (Colleen number 6) 35
7℃ [675'F]・・・・・・・・・・・・・15 minutes (6) Directly quench with ambient temperature water・・・・・・・・・・・・・
・・・・・・2 minutes (7) Organic pickling solution C (Colleen rK
GCJ organic acid) 66°C (150°F)
・5 minutes (8) Rinse with fresh water and force dry...
Result: The spinneret had the same appearance as after step 1 (4). Approximately 4 holes had loosely adhered residue. Approximately 250 grams of polymer was removed.

Example V "One spinneret with mild polyester polymer residue remaining.

0 Nitrate-Based Molten Salt Bath A (Colleen Number 6) Processed as outlined in Example IV above, except that the salt temperature was 371"C: (700°F).

The results were marginally good, with only one hole having a small amount of residue. The total weight of polymer removed was approximately 125 grams (0
, 251bs).

Example Vl 1 spinneret with "light" polymeric residue.

Process as outlined in steps (1) to (4) of Example 3.

The test results showed that there was a residue.

The spinneret was then bathed in nitrate-based molten salt bath B (Colleen DGS).
for 15 minutes at 427° C. (800° F.), then quenched with water, pickled with organic pickling solution CI-KGC, rinsed with water, and dried.

Result: The spinneret was cleaned in a salt bath and treated with organic pickling solution CrKGCJ.
) After pickling, it had a bright metallic luster appearance. Inspection after this treatment revealed loosely adhered residue in three holes.

Example vn Clasp type annular spinneret nitrate based molten salt bath A, 316°G (600°F)...
...Post-cooling in still air for 5 minutes...---River...
・・Old −−−−−−−−−−−i minute rapid cooling with water at ambient temperature ・・・・・・・・・・・ Old ・・・・・・・・・・・・
Rinse with warm water for 30 seconds...
・・・・・・・・・・・・・・・ Old・・・・・・ 2 minutes result:
The polymer was completely removed. The material has a dark grey-black appearance, probably due to previous cleaning methods.

Approximately 2.5 grams of polymer was removed.

Examples ■ Square spinneret plate coated with polyester polymer residue.

Nitrate-based molten salt bath AC Colleen number 6) 316℃ (
600°F) −・−・−・−・−10 minutes post-cooling in still air・・・・・・・・・・・・・・・・・・
・・・・・・・・・−・Quick cooling with water at ambient temperature for 2 minutes−・
・・・・・・－・・・・・・・・・・・・・・・・・・
Rinse with warm water for 30 seconds...
・・・・・・・・・・・・・・・・2 minutes 10% organic pickling liquid (rKGCJ) mixture at 66℃ (150℃
)・・・・・・・・・Rinse with water for 5 minutes and air dry.

Results: The polymer was removed from the "central" capillary, but the peripheral capillaries still had some polymer residue. Oxidation in a salt bath completely removed the polymer, leaving the constituents with a bright metallic luster.

The above cycle was repeated and the additional polymer was removed, but there was still a small amount of residual polymer in the surrounding capillaries.

The bath temperature was raised to 343°C (650°F) and the spinneret was soaked again for 5 minutes, but the remainder of the cycle was as described above. All polymers were removed and the spinneret had a shiny metallic appearance.

Examples ■ Specimen description = 5 stainless steel spinnerets, 1 crusher plate, 1 "spreader" plate Specimen processing overview: Initial tests were conducted with molten salt in nitrate-based molten salt bath A at temperature The range was 316°C to 343°C (600°C to 650°F). Immersion times range from 30 minutes to 60 minutes. Following salt bath cleaning, the components were quenched and rinsed in ambient temperature water, then dried in water [temperature = 71°C (160') to remove solidified salt residues.
In the case of Fl], the sample was briefly immersed for about 5 minutes.

The cleaning results were compared to those obtained in Examples rV, V, V[, i.e. approximately 90-95% of the holes were completely cleaned, whereas the other examples had no residual polymer and/or There was charred material.

Four spinnerets of relatively small diameter along with a relatively large, thick spinneret are placed in a nitrate-based molten salt bath A for a second time.
The same conditions as the first time were used except that vibration was added during the processing step. As a result, 100% of the skin was cleaned.

Conclusions for the Examples: Example I is representative of an average size and spacing spinneret with average length to width ratios.

A single treatment removes most of the polymer, but not all of it. A second treatment with the same salt then removes all remaining polymers.

Example Ir is similar to Example 1 but shows how the soaking time can be reduced by 4 if the temperature of the bath is slightly changed during the second cycle.

Example I shows the use in a spinneret of rather large orifices with relatively low length-to-diameter ratios, but even in this case there was still some residue in some orifices.

Examples ■ to ■ show how changing certain conditions improves the effectiveness of the treatment.

In Example 1, the temperature for the first run was 343°C (650°F) and the second time was 357°C (675'Fl).

There was still significant residue after both cycles.

In Example V, the bath temperature was raised to 371°F (700°F) and significant improvement was obtained, but there was still residue in one orifice. In Example 2, the first bath was salt bath agent B rather than nitrate salt bath agent A. This nitrate-based salt bath agent B (DGS) is a little stronger and has a temperature of 427°C (800°C).
The orifice was thoroughly cleaned.

Example 2 shows the case of a spinneret with a very large orifice with a very low length-to-diameter ratio.

In this case, all the polymers could be removed in just one treatment.

Example 3 is an example of a spinneret in which the inner or central orifice has a smaller length-to-diameter ratio than the outer orifice. In this case, the first cycle removed all of the polymer from the inner orifice, but a residue remained in the outer orifice.

The second cycle removed most of the residue, but a third cycle was required to completely clean all orifices.

Example ■ shows the vibration used to facilitate the process.

The orifice had a high length-to-diameter ratio, and the second cycle was not expected to be completely effective, but the vibration completely cleaned the orifice.

Examples IV through (1) also demonstrate the use of organic pickling solution C (KGC), which acts to aid in removing loose residue.

Several experiments were conducted to clean clogged holes in a spinneret to demonstrate the different angular effects of hole inclination during processing.

The spinneret is made of 17-4PH steel and has a diameter of approximately 0.64m.
m (0,02 inches) length approx. 1,50 mm (0,06
There are 420 holes.

In each case polyester spherules are placed in a cold spinneret;
The holes in the spinneret are completely free and unclogged. The spinneret was placed in a 300° C. furnace for 45 minutes to allow the polymer to melt and plug the pores. The spinneret was removed from the furnace and allowed to cool for 30 minutes. In each test, the spinnerets were processed in the same manner except for the angle of inclination of the holes. That is, it was placed in a salt bath of nitrate salt bath agent A for 10 minutes at 343°C (650°F).

Each cap is then quenched with water at ambient temperature, followed by organic pickling solution C.
(KGC) Acid cleaned to brighten the surface and then water rinsed. The angle of the holes with respect to the horizontal and the amount of cleaning are as follows: 7 The test results of tests X to XVI are shown schematically in a single shape. It is clear that the optimum angle is between 45° and 60°, with angles between 30° and 75° also working well. It is also clear that in this range the larger end should be directed upwards.

The effect of the orientation of the orifice, or hole, is not completely known, but by holding the orifice at an angle with the large end up, gas can escape through the top and not be trapped, and molten salts can also It is also believed that the trapped gas can enter unhindered.

[Brief explanation of drawings]

The accompanying figure is a graph showing the cleaning rate of the spinneret orifice at different angles from the horizontal.

Claims (21)

[Claims] 1. As a method of cleaning organic substances adhering to the orifice of a spinneret, the spinneret is immersed in an oxidizing molten salt bath maintained at a temperature of 260° C. to 482° C., and the spinneret is trapped inside. The spinneret is positioned such that the orifice extends at an angle of 30 to 75 degrees with respect to the horizontal and the entrance end of the orifice is in an upward orientation to permit release of the A method for cleaning a spinneret, comprising the steps of removing the spinneret from a molten salt bath and then rapidly cooling the spinneret. 2. The method for cleaning a spinneret according to claim 1, wherein the angle of the orifice is from 45 degrees to 60 degrees. 3. The method of cleaning a spinneret according to claim 1 further comprising: adding at least one additional immersion of the spinneret in an oxidizing molten salt bath maintained at a temperature of 260° C. to 482° C.; The cap is arranged such that the orifice extends at an angle such that gas trapped therein can be released and particles are not deposited within the orifice, with the entrance end of the orifice pointing upward. , retaining the spinneret in the molten salt bath for an additional period of time until observable phenomena evidencing a reaction cease, and removing the spinneret from the molten salt bath. A method for cleaning a spinneret, comprising: 4. The method of cleaning a spinneret according to claim 1, wherein the molten salt bath is maintained at a temperature of 260°C to 371°C. 5. 5. The method of cleaning a spinneret according to claim 4, wherein the molten salt bath contains an alkali metal nitrate. 6. 6. The method of cleaning a spinneret according to claim 5, wherein said molten salt bath comprises about 58.8% potassium hydroxide and about 40% potassium hydroxide.
A method for cleaning a spinneret comprising 3% sodium nitrate and about 0.9% potassium permanganate. 7. A method for cleaning a spinneret according to claim 1, characterized in that said spinneret is vibrated during treatment with said molten salt bath. 8. 4. The method for cleaning a spinneret according to claim 3, wherein the second molten salt bath is maintained at a higher temperature than the first molten salt bath. 9. 9. The method of cleaning a spinneret according to claim 8, wherein the first molten salt bath is at a temperature of from 260<0>C to 371<0>C;
A method for cleaning a spinneret, characterized in that the second molten salt bath is maintained at a temperature of 371°C to 482°C. 10. 4. The method of cleaning a spinneret according to claim 3, wherein the plurality of molten salt baths contain an alkali metal nitrate. 11. 10. The method of cleaning a spinneret according to claim 9, wherein the first molten salt bath comprises potassium hydroxide and sodium nitrate, and the second molten salt bath comprises sodium nitrate, sodium hydroxide, sodium chloride, and water. A method for cleaning a spinneret characterized by comprising potassium oxide. 12. The method for cleaning a spinneret according to claim 10,
A method for cleaning a spinneret, wherein at least the first molten salt bath comprises potassium hydroxide and sodium nitrate. 13. The method for cleaning a spinneret according to claim 12,
A method for cleaning a spinneret, wherein at least the first molten salt bath comprises 58.8% potassium hydroxide, 40.3% sodium nitrate, and 0.9% potassium permanganate. 14. The method for cleaning a spinneret according to claim 11,
The first molten salt bath comprises about 58.8% potassium hydroxide, about 40.3% sodium nitrate, and about 0.9% potassium permanganate; 15
% sodium nitrate and about 10% sodium chloride,
A method for cleaning a spinneret characterized by comprising about 12% potassium hydroxide and the balance sodium hydroxide. 15. 4. The method of cleaning a spinneret according to claim 3, wherein the spinneret is vibrated during at least one of the plurality of steps of immersing the spinneret in the molten salt bath. 16. 2. The method for cleaning a spinneret according to claim 1, wherein the spinneret is washed with water by immersion in an organic acid after the quenching. 17. 4. The spinneret cleaning method according to claim 3, wherein the spinneret is immersed in the second molten salt bath and then rapidly cooled, followed by water washing by immersion in an organic acid. 18. As a method for removing organic substances attached to a material to be treated, the material to be treated is immersed in a first molten salt bath maintained at a temperature lower than 371°C and higher than 260°C. , the material to be treated is kept in the molten salt bath until a phenomenon indicating a reaction occurs and then substantially stops;
The material to be treated is immersed in a second oxidizing molten salt bath maintained at a temperature lower than 82° C. and higher than 371° C., and the material to be treated is immersed in the molten salt bath until a phenomenon indicating a reaction occurs and then substantially stops. A method for cleaning a spinneret, characterized in that it comprises the above-mentioned steps of holding the spinneret in a salt bath. 19. The method for cleaning a treated material according to claim 18,
A method for cleaning a material to be treated, characterized in that the molten salt bath contains an alkali metal nitrate. 20. 19. The cleaning method according to claim 18, wherein the first
A cleaning method characterized in that the molten salt bath comprises potassium hydroxide and sodium nitrate, and the second molten salt bath comprises sodium nitrate, sodium hydroxide, sodium chloride and potassium hydroxide. 21. 19. The cleaning method of claim 18, wherein the first molten salt bath comprises about 58.8% potassium hydroxide and about 40% potassium hydroxide.
3% sodium nitrate, about 0.9% potassium permanganate, and a second molten salt bath containing about 15% sodium nitrate, about 10% sodium chloride, and about 12% potassium hydroxide. and the remainder being sodium hydroxide.