Method for handling water-sensitive and / or temperature-sensitive compounds

Abstract

The present invention provides a method for the transport and storage of water- and / or temperature-sensitive compounds, such as isocyanates, where the compounds can be stored or transported under controlled conditions and are easy to remove and subsequently clean without risk of damaging containers or pipes. To this end, the present invention is directed to a method for handling liquid water- and / or temperature-sensitive compounds. A water-soluble coating is applied to the surface of a device that will come into contact with the liquid water- and / or temperature-sensitive compound, and the coating is dissolved with water to clean the device. The water-soluble coating preferably comprises polyvinyl alcohol.

Description

[Technical field]

[0001] The present disclosure is directed to a method for transporting and storing liquid water- and temperature-sensitive compounds, such as isocyanates, and to suitable equipment, such as containers and pipes, for this method. [Background technology]

[0002] Isocyanates are sensitive to water, crystallization and overheating. Therefore, transportation and storage must be done in a water-free atmosphere and at controlled temperatures. If one or more of these conditions are violated, polyurea and / or crystallized and / or decomposed isocyanate will deposit on the inside walls of containers, pipes or equipment.

[0003] On-site, these contaminated containers and pipes are cleaned by steam heating, followed by mechanical cleaning with high pressure water, or cleaning with grinding equipment or reactive chemicals. Needless to say, such cleaning often causes damage to the containers or pipes. Moreover, when chemicals are used, the wastewater must be treated as chemical waste.

[0004] Several publications are directed to methods for removing isocyanate residues from pipes and equipment during isocyanate production. For example, European Patent Specification EP-2772528 describes a specific solvent composition comprising a polyol, an inorganic base and an amine. This solvent composition dissolves the isocyanate residues.

[0005] US Pat. No. 5,506,301 describes treating isocyanate distillation residue with a mixture of acidified water and an organic compound, such as limonene, limonene oxide, menthoxyacetic acid, menthyl chloroformate, or gamma-terpinene, and stirring until the mixture has a pH of 7.

[0006] In US Patent Application Publication US2012 / 0271067, isocyanate residues are contacted with water and a solvent at high pressure and temperature to decompose the isocyanate residues.

[0007] Publications relating to the transportation of isocyanates describe tank containers equipped to meet the needs of transporting liquids that can solidify, are highly viscous, and react easily with water. For example, Japanese Patent Publication No. 2002-053196 describes a tank container divided into multiple heating sections equipped with heating means and temperature sensors.

[0008] Chinese Patent Publication No. CN210392211 describes a container barrel with a polyethylene lining bag for the transportation of blocked isocyanates.

[0009] US Patent Application Publication No. US2010 / 032337 discloses a receptacle or container adapted for the storage and transport of selected substances or items, including liquid, gel, or solid substances. These selected items or substances may be either hazardous or non-hazardous substances. As used herein, hazardous substances (or hazardous materials) generally refer to substances that are potentially toxic or detrimental to human health or the environment. The receptacle or container has a multi-layer structure, where the inner layer may be in the form of a material that dissolves or degrades when in contact with a suitable solvent, such as water or a cleaning composition. This disclosure does not refer to a method for handling water- or temperature-sensitive substances, but rather a method for handling hazardous substances, such as pesticides. UK Patent Application Publication No. GB2237 is also directed to a container for hazardous substances. Summary of the Invention [Means for solving the problem]

[0010] The present invention is a method for the transport and storage of water-sensitive and / or temperature-sensitive compounds, such as isocyanates, where the compounds can be stored or transported under controlled conditions, facilitating removal and subsequent cleaning of the compounds without risk of damaging containers or pipes.

[0011] To this end, the present invention is directed to a method for handling a liquid water-sensitive and / or temperature-sensitive compound, in which a water-soluble coating is applied to the surface of a device that comes into contact with the liquid water-sensitive and / or temperature-sensitive compound, and the coating is dissolved with water to clean the device.

[0012] In one aspect, the water-sensitive and / or temperature-sensitive compound in liquid form is removed from the device in liquid form after handling.

[0013] The water-soluble coating preferably comprises polyvinyl alcohol.

[0014] The handling includes the transportation, storage, production and / or purification of the water-sensitive and / or temperature-sensitive compounds in liquid form.

[0015] Examples of said water-sensitive and / or temperature-sensitive compounds in liquid form are isocyanates, preferably diisocyanates, such as methylene diphenyl diisocyanate or toluene diisocyanate.

[0016] The device referred to may comprise any other functional equipment that comes into contact with the compound being handled, such as, for example, containers, tanks, pipes, valves, or any combination thereof, including the above mentioned functional equipment.

[0017] The water-soluble coating may be removed by dissolving the water-soluble coating in water.

[0018] Optionally, the surface having the water-soluble coating thereon is treated with steam prior to dissolving the water-soluble coating to clean the surface that has been in contact with the water- and temperature-sensitive compound.

[0019] Debris remaining after the removal of the water-sensitive and / or temperature-sensitive compound is washed away during the removal of the water-soluble coating.

[0020] Optionally, the device is provided with temperature control means and means to prevent water from entering the compound during said handling.

[0021] The present invention is also directed to a device for handling liquid water-sensitive and / or temperature-sensitive compounds, said device being equipped with temperature control means and means for preventing water from entering said compounds during said handling, and said surfaces of the device in contact with said liquid water-sensitive and / or temperature-sensitive compounds being provided with a water-soluble coating, preferably a polyvinyl alcohol coating, as well as to a method of using said device for handling said liquid water-sensitive and / or temperature-sensitive compounds. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present invention is directed to a method for handling a liquid water-sensitive and / or temperature-sensitive compound, wherein a water-soluble coating is applied to a surface of a device that will come into contact with the liquid water-sensitive and / or temperature-sensitive compound, and the coating is dissolved with water to clean the device.

[0023] In the context of this specification, "water-sensitivity" means water-reactivity, hygroscopicity, dehydration, crystallization, or any other physical or chemical phenomenon caused by water or moisture that has a detrimental effect on a compound.

[0024] In the context of this specification, the term "temperature sensitive" means a change in temperature that has a detrimental effect on a compound.

[0025] In one aspect, the water-sensitive and / or temperature-sensitive compound in liquid form is removed from the device in liquid form after handling.

[0026] In principle, can be applied as a protective coating that is stable under the conditions applied during handling; and Does not interfere with the compounds being handled; Of course, it is water soluble under the conditions applied during removal. Any material may be used as the water-soluble coating. Examples of suitable water-soluble coatings are polyvinyl alcohol and its derivatives, such as ethoxylated PVA, cellulose and its derivatives, such as carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, starch, polyglycolic acid, polyethylene glycol, polypyrrolidone, polyhydroxybutyrate, and copolymers or blends thereof.

[0027] The water-soluble coating preferably comprises polyvinyl alcohol. It has been found that the polyvinyl alcohol-containing coating can be easily applied to the inside of equipment made of either steel, plastic or composite materials to form a protective coating. The polyvinyl alcohol-containing coating is resilient to many water- and / or temperature-sensitive compounds. Furthermore, the polyvinyl alcohol-containing coating can be easily removed with water without damaging the surfaces that have come into contact with the water- and / or temperature-sensitive compounds. Moreover, the wastewater formed during cleaning contains only dissolved polyvinyl alcohol-containing coating and can be treated as a biodegradable wastewater stream.

[0028] Suitable polyvinyl alcohol-containing paints are commercially available in various grades. The solubility of the PVA coating depends on the degree of hydrolysis and its molecular weight. Depending on the handling conditions, a suitable PVA grade can be selected. In general, PVA with a degree of hydrolysis of 70-99% can be used. To ensure a suitable coating and at the same time a suitable water-solubility rate upon removal, a degree of hydrolysis of 80-98% is preferred, more preferably a degree of hydrolysis of 85-96%, most preferably a degree of hydrolysis of 90-94% is used. The molecular weight is 10,000 to 150,000 (Mw). Blends of PVA with other polymers are also suitable, for example blends of polyvinylpyrrolidone, polyethylene glycol, polylactic acid, polycaprolactone, polyethylene glycol, polysuccinic acid can be used as long as the solubility of the resulting coating is satisfactory and does not interfere with the product being handled. Also copolymers of vinyl acetate and monomers of the above-mentioned polymers can be used.

[0029] The PVA-containing coating may contain additives, such as additives to improve the adhesion of the coating, coatability, the mechanical or chemical stability of the coating, or solubility during washing. Any conventional additive may be used in the present invention, but care must be taken that the wastewater remains a biodegradable wastewater stream. Suitable additives may be biodegradable plasticizers, biodegradable defoamers, surfactants, biocides, and the like.

[0030] The handling may include the transportation, storage, manufacture, and / or purification of liquid water-sensitive and / or temperature-sensitive compounds.

[0031] Examples of liquid water- and / or temperature-sensitive compounds are isocyanates, preferably methylene diphenyl diisocyanate or phenyl diisocyanate.

[0032] Isocyanates are sensitive to water, crystallization and overheating. In the process according to the invention, these isocyanates can be produced, transported, purified and stored in a water-free atmosphere and under controlled temperature. If one of the above conditions is violated, polyurea and / or crystallized isocyanate and / or decomposed isocyanate will be deposited on the water-soluble coating and can be removed without damaging the surface of the device that came into contact with the isocyanate.

[0033] The device referred to may comprise a container, a tank, a pipe, a valve, any other functional apparatus that comes into contact with the compound being handled, or a combination thereof.

[0034] Optionally, said device is provided with temperature control means and means to prevent water from entering said compound during said handling.

[0035] In the transportation, production and purification of isocyanates, it is common, for example, to discard pieces of functional equipment, such as valves, flanges, pipes, manhole covers, upon cleaning. With the method and apparatus according to the invention, this is not necessary.

[0036] As mentioned above, the water-soluble coating may be removed by dissolving the water-soluble coating in water. The water pressure to dissolve the coating may vary from about 10 to about 200 bar, preferably from 50 to 90 bar. Usually, a water sprayer with a water pressure of about 70 bar is sufficient. Optionally, water with an elevated temperature (e.g., 30 to 80° C.) is used to facilitate and / or accelerate the dissolution of the coating.

[0037] Optionally, before dissolving the water-soluble coating to clean the surface that was in contact with the water-sensitive and temperature-sensitive compounds, the water-soluble coated surface is treated to remove residual water-sensitive and / or temperature-sensitive compounds. Optimally, a treatment is selected to solidify the compounds to facilitate removal of the residual compounds. For example, in the case of compounds that react with water to form solids, treatment with steam or hot water is possible. To facilitate processing, steam treatment is preferred. One advantage of steam treatment is that no chemical wastewater is generated. This treatment is particularly suitable when dealing with isocyanates. Any isocyanates remaining after removal will be hydrolyzed by steam treatment to form solid polyurea. This solid polyurea debris is subsequently washed away during solubilization of the water-soluble coating for cleaning.

[0038] Depending on the above water and temperature sensitivity of the compound, an appropriate treatment of the residual compound, such as heat treatment, cooling / crystallization treatment, etc., can be selected.

[0039] Any debris remaining after removal of the water-sensitive and / or temperature-sensitive compound or after the treatments described above is washed away during removal of the water-soluble coating. Larger debris may be removed by hand.

[0040] The present invention is also directed to a device for handling liquid water-sensitive and / or temperature-sensitive compounds, said device being equipped with temperature control means and means for preventing water from entering said compounds during said handling, and said surfaces of the device in contact with said liquid water-sensitive and / or temperature-sensitive compounds being provided with a water-soluble coating, preferably a polyvinyl alcohol coating, as well as to a method of using said device for handling said liquid water-sensitive and / or temperature-sensitive compounds.

[0041] The isocyanates are stored and / or transported in containers or pipes which are provided with an internal coating containing water-soluble polyvinyl alcohol. After removal of the isocyanates, the containers / pipes can be easily washed with water at relatively low pressure (about 70 bar). The remaining isocyanates are hydrolyzed to form solid polyurea. The PVA-containing coating dissolves and the solid polyurea and other precipitates are washed away. The solids can be easily separated from the waste water and the waste water can be treated as a non-chemical waste water. It has been found that the PVA-containing coating used in the examples below does not impair the quality of the isocyanates, while the containers and / or pipes are protected from the isocyanates. This and the fact that harsh mechanical or chemical cleaning can be omitted increases the life of the containers and / or pipes and reduces the CO2 emissions of safe energy and cleaning. 2 It will reduce the footprint.

[0042] The present invention is further elucidated by the following examples, which are intended for illustrative purposes and should not be construed as limiting.

[0043] Working Example

[0044] Example 1: Flow test of PVA-coated stainless steel plate using MDI

[0045] A commercially available PVA coating was applied to stainless steel specimens. A portion of the specimens was left untreated. After application of the coating, the specimens were placed in a steel container partially filled with MDI (Iso-PMDI 92340).

[0046] The MDI was pumped over the specimen at a flow rate of 1.65 m / s and a distance of ±3 cm. The flow rate was 30 m / h. 3 This corresponds to the outflow rate from the dip tube of an MDI tank container in which the liquid is filled.

[0047] The pump was pulsed, so the effect of MDI would actually be greater. The pump was operated for a total of 174 hours, i.e. 7 days, at a temperature of about 30° C. and ambient humidity. Over time the MDI thickened.

[0048] After the flow test, the test specimens were subjected to a steam treatment. The MDI adhering to the surface reacted and hardened. After steaming, the test specimens were washed with 10°C water at 90 bar pressure water sprayer.

[0049] During the flow test, the PVA coating remained fixed on the surface of the specimen. During the steam treatment, the residual MDI hardened but could be easily removed with a pressure water sprayer. On the untreated surface, the MDI could not be removed and the surface could not be properly cleaned.

[0050] Example 2: As in Example 1, but using a composite plate

[0051] The test described in Example 1 was repeated using fiberglass-vinyl ester composite specimens in place of the stainless steel specimens.

[0052] The results are similar to those of Example 1.

[0053] Example 3: PVA-coated stainless steel tank container

[0054] The samples are actual stainless steel tank containers that are cleaned and dried prior to testing.

[0055] At the bottom of the tank, different commercial PVA coatings, each with different water solubility, were applied. Once the coatings were applied and dried, approximately 60 liters of pMDI type was poured into the tank container, which corresponds to the remaining amount of MDI in the tank after shipping.

[0056] The tank container with residual MDI was subjected to steam treatment for approximately 8 hours. The temperature and steam caused the MDI to react and harden. Large pieces of hardened MDI were removed by hand. After cleaning the tank with a broom, a standard washing program with water (100 bar and 70-80°C for 5 minutes) was used to clean the tank.

[0057] After steam cleaning, no MDI remained in the steel container where the coating had been applied. The steel tank was intact.

[0058] Where the NO coating was applied, the MDI did not peel off even after being steam cleaned with water at 100 bar and 70-80°C for 5 minutes.

[0059] All three different types of coatings proved effective.

Claims

1. A method for handling liquid water-sensitive and / or temperature-sensitive compounds, the method comprising applying a water-soluble coating to a surface of a device that will come into contact with the liquid water-sensitive and / or temperature-sensitive compound, and dissolving the coating with water to clean the device.

2. The method of claim 1 , wherein the water-sensitive and / or temperature-sensitive compound in liquid form is removed from the device in liquid form after handling.

3. The method of claim 1 or 2, wherein the water-soluble coating comprises polyvinyl alcohol.

4. 3. The method of claim 1 or 2, wherein said handling comprises transporting, storing, producing and / or purifying said water-sensitive and / or temperature-sensitive compound in liquid form.

5. 3. The method according to claim 1, wherein the water-sensitive and / or temperature-sensitive compound in liquid form is an isocyanate.

6. The method of claim 5, wherein the liquid water-sensitive and / or temperature-sensitive compound is methylene diphenyl diisocyanate or toluene diisocyanate.

7. 3. The method of claim 1 or 2, wherein the device is equipped with any other functional equipment that comes into contact with the compound to be handled.

8. The method of claim 1 or 2, wherein the device comprises a container, a tank, a pipe, a valve, or a combination thereof.

9. 3. The method of claim 1 or 2, wherein the water-soluble coating is removed by dissolving the water-soluble coating in water.

10. 8. The method of claim 7, wherein the surface having a water-soluble coating thereon is treated with steam prior to dissolving the water-soluble coating to clean the surface that has been in contact with the water-sensitive and / or temperature-sensitive compound.

11. 3. The method of claim 1 or 2, wherein debris remaining after said removal of said water-sensitive and / or temperature-sensitive compound is washed away during said removal of said water-soluble coating.

12. 3. A method according to claim 1 or 2, wherein the device is provided with temperature control means and means to prevent water from entering the compound during said handling.

13. A device for handling liquid water-sensitive and / or temperature-sensitive compounds, the device being provided with temperature control means and means for preventing water from entering the compound during handling, and the surface of the device which comes into contact with the liquid water-sensitive and / or temperature-sensitive compound being provided with a water-soluble coating.

14. 14. A device for handling liquid water-sensitive and / or temperature-sensitive compounds according to claim 13, wherein the water-soluble coating is a polyvinyl alcohol-containing coating.

15. The device according to claim 13 or 14, wherein the device is a functional apparatus.

16. The device described in claim 13 or 14, wherein the device is a container, a tank, a pipe, or a valve, or a combination thereof.

17. 15. Use of a device according to claim 13 or 14 for handling liquid water-sensitive and / or temperature-sensitive compounds.