CN111333911A

CN111333911A - Red mud treating agent based on grafted wax and preparation method and application thereof

Info

Publication number: CN111333911A
Application number: CN201811556628.4A
Authority: CN
Inventors: 杨建强
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-12-19
Filing date: 2018-12-19
Publication date: 2020-06-26

Abstract

The invention relates to a red mud treating agent based on grafted wax, a preparation method and application thereof. The red mud treating agent is grafted wax with branched chain containing carboxyl, and can be regarded as a long-chain organic acid structure. Therefore, the composite material can be used as an in-situ dealkalizing agent of the red mud, an acid reactant or a complexing agent of metal oxides in the red mud and a surface modifier of the red mud. The red mud can be used as a functional filler for toughening, lubricating and reinforcing resin and plastic processing. The free sodium hydroxide in the red mud is neutralized in situ to generate the sodium salt of the long-chain organic acid, which plays a certain role in improving the performance of the plastic products. It also has an internal lubricating action, thereby improving the processability of the resin.

Description

Red mud treating agent based on grafted wax and preparation method and application thereof

Technical Field

The invention relates to a red mud treatment agent based on grafted wax, a preparation method and application thereof, and the treated red mud can be used as a functional filler for plastic processing, belonging to the technical field of comprehensive utilization of red mud.

Background

The red mud is pollution waste residue (called red mud because of iron oxide content and iron red development), which is discharged from alumina industry, and the main components of the red mud are oxides of iron, calcium and silicon and residual free NaOH. It is estimated that about 0.8-1.6t of red mud is produced per 1t of alumina produced. The red mud generated by the alumina industry all over the world every year exceeds 6000 million t, the annual discharge amount of the red mud in China is about 3000-4000 million t at present, the accumulated red mud accumulation amount reaches hundreds of millions of tons, all the red mud is stockpiled in the open air, and most of the stock dump dams are stored by a red mud warehouse wet method or a dehydration drying treatment method at present, so that the farmland is invaded, alkali in the red mud permeates to the underground, and the underground water body and soil pollution is caused; meanwhile, dust formed by the naked red mud flies with wind, pollutes the atmosphere and deteriorates the ecological environment; in addition, valuable components in the red mud are not fully utilized, and resource waste is caused. Therefore, comprehensive utilization and harmless treatment of the waste water are necessary; however, the industrial application of the red mud is very little due to the high alkali content of the red mud, and the comprehensive utilization rate is only about 10 percent.

Red mud is less reported as a filler for plastic articles. The previous reports mainly use the red mud as the functional filler of the polyvinyl chloride. Besides the function of the filler, the alkalinity of the alkaline metal oxide in the red mud is utilized to absorb the hydrogen chloride generated by the decomposition of the polyvinyl chloride and inhibit the decomposition of the polyvinyl chloride, and the prepared PVC plastic is called as 'red mud plastic'. The technology is firstly developed successfully by Taiwan combined industrial research institute, but is not well popularized.

Some patent documents report, for example: the Chinese patent document CN1047512A utilizes recycled plastics and wood chips and red mud to be extruded by a screw extruder to prepare the wood chips and red mud modified plastics. Chinese patent document CN102070815A describes that red mud is used as a flame retardant, maleic anhydride grafted polyethylene (grafting rate is 5-10%) or an ethylene-vinyl acetate copolymer is used as an in-situ dealkalizing agent, and the in-situ dealkalizing agent and polyethylene are melted and blended in a mixing roll to obtain a finished product of the flame-retardant polyethylene plastic. Chinese patent document CN106751170A is a colored single-wall or double-wall corrugated tile made of red mud and PVC resin. However, in these techniques, the red mud is directly used as a filler of a plastic product without being treated, and the dispersibility of the red mud in a plastic melt is poor, so that the obtained plastic product has poor mechanical properties, and only some products with low mechanical property requirements can be manufactured. The main reasons are as follows: firstly, the application in plastic products is seriously affected by more sodium hydroxide carried by the red mud. The inorganic salts formed, if neutralized simply with mineral acids, also severely reduce the mechanical properties of the plastic article and the useful life of the article. Secondly, the red mud particles have complex components, the compatibility between the inorganic particles and resin is poor, the surface area is small (compared with the porous filler), and the comprehensive performance of the plastic product can be reduced. Therefore, the poor dispersibility of the red mud particles in the resin and the damage of free NaOH carried by the red mud to the plastic products are two main reasons that the red mud cannot be widely used as a filling agent of the plastic products.

Waxes like petroleum waxes, polyethylene waxes, polypropylene waxes, and fischer-tropsch waxes, which have started to be produced on a large scale in the last few years, are available from a wide variety of sources and are inexpensive, and they are often used as lubricating aids in resin extrusion processing, but the addition of waxes sometimes reduces certain mechanical properties. This is because the wax merely reduces the frictional force at the interface between the inorganic filler and the resin, and fails to increase the intermolecular force therebetween. Several modifications have been made to waxes to increase compatibility between them, such as oxidation of the wax to bring it with a few carboxyl groups, grafting of the wax to bring it with polar groups, but generally the grafting rate is not high.

At present, the graft modified wax is not reported to be used for treating the red mud and used as a filling material of plastic products.

Disclosure of Invention

Aiming at the defects of the prior art, particularly the problem of poor dispersibility when the red mud is directly used as a plastic product filler, the invention provides a red mud treating agent based on grafted wax, and a preparation method and application thereof. The wax (petroleum wax, Fischer-Tropsch wax, polyethylene wax, polypropylene wax) is graft copolymerized with unsaturated acid or its ester (such as butenedioic acid monoester) to obtain graft modified wax with branched chain containing carboxyl group, so that the graft modified wax has certain properties of the coupling agent. The modified wax is used for treating red mud and is used as a functional filler in resin processing, the first function is to serve as an in-situ neutralizing agent to neutralize free sodium hydroxide in the red mud to form long-chain organic acid sodium salt, the second function is to serve as a transition metal salt or a complex with long-chain organic groups with transition metal oxides in the red mud, and the transition metal salt and the long-chain organic acid sodium salt both have the functions of reducing the interfacial energy of the red mud and the resin and increasing the compatibility of the red mud and the resin, so that the mechanical property of a plastic product is improved. They have obvious internal lubrication effect on a resin system and can improve the processability of the resin and red mud system.

The preparation of the treating agent and the process of treating the red mud do not produce secondary environmental pollution.

The technical scheme of the invention is as follows:

the red mud treating agent is a graft modified wax with a branched chain containing carboxyl.

According to the present invention, it is preferable that the graft ratio of the branched carboxyl group-containing graft-modified wax is 1.0 to 8.0% and the acid value is 10 to 80g KOH/100g graft-modified wax.

According to the present invention, it is preferable that the branched carboxyl group-containing graft-modified wax is obtained by graft-copolymerizing a wax with an unsaturated acid or an unsaturated acid derivative.

According to the invention, the wax is preferably a petroleum wax, a Fischer-Tropsch wax, a polyethylene wax or/and a polypropylene wax.

According to the invention, it is preferred that the unsaturated acid is butenedioic acid, acrylic acid or/and methacrylic acid;

preferably, the derivative of the unsaturated acid is maleic acid monoester or maleic anhydride; further preferably, the butenedioic acid monoester is a butenedioic acid monoester obtained by ring-opening reaction of maleic anhydride and alcohol; the alcohol is monohydric alcohol with 1-20 carbon atoms, dihydric alcohol with 2-8 carbon atoms, trihydric alcohol with 3-8 carbon atoms or a mixture of the monohydric alcohol and the dihydric alcohol.

According to the invention, the preparation method of the red mud treatment agent based on the grafted wax comprises the following steps:

mixing wax with unsaturated acid or unsaturated acid derivative and initiator, and graft copolymerizing at 165-180 deg.c.

According to the preparation method of the invention, the graft copolymerization reaction is preferably carried out by melt extrusion in an extruder, and the temperature of each zone of the extruder is 165-180 ℃ and the retention time is 15-45 min. The graft ratio of the obtained graft-modified wax is 1.0-8.0%, and the acid value is 10-80g KOH/100g graft-modified wax. Further preferably, the graft ratio is 2.0 to 4.0%.

According to the invention, the application of the red mud treatment agent is used for treating red mud.

According to the invention, the method for treating the red mud by using the red mud treating agent comprises the following steps:

adding the red mud treatment agent into water, heating, stirring, dispersing and emulsifying, and then uniformly adding the red mud treatment agent into the water-containing red mud to be treated; after the reaction is sufficient, the red mud is centrifugally dehydrated, dried, crushed and sieved to obtain the treated red mud.

Further preferably, the heating temperature is 60-90 ℃, and the mixture is sieved by a 800-1000-mesh sieve.

According to the invention, preferably, the addition amount of the red mud treatment agent is 6-25% of the mass of the water-containing red mud; preferably, the mass content of the hydrous red mud water is 30-50%. More preferably, the red mud treated by the red mud treatment agent is added in an amount of 3-15%, more preferably 3-10%, on a dry basis.

According to the invention, the red mud treated by the red mud treating agent is used for processing resin instead of light calcium carbonate as a filler. Can obviously improve the melt index of the resin and can improve the mechanical properties of certain plastic products.

According to the invention, the red mud treated by the red mud treatment agent is used as a filling material in the processing process of resin products, and the addition amount of the treated red mud is 20-60% of the mass of the resin raw material.

According to the invention, the red mud masterbatch is prepared by adding resin into red mud treated by the red mud treatment agent and performing melt extrusion, and the mass content of the red mud in the red mud masterbatch is 50-90%.

According to the present invention, preferably, the resin is polyethylene, polypropylene or polyvinyl chloride.

The red mud of the invention can be sintering process red mud or Bayer process red mud.

In the present invention, the red mud treatment agent is a branched chain carboxyl-containing graft wax, and can be considered as a long-chain organic acid structure. Therefore, the composite material can be used as an in-situ dealkalizing agent of the red mud, an acid reactant or a complexing agent of metal oxides in the red mud and a surface modifier of the red mud. The red mud can be used as a functional filler for toughening, lubricating and reinforcing resin and plastic processing. The method is characterized in that free sodium hydroxide of red mud is neutralized in situ to generate sodium salt of long-chain organic acid, and the sodium salt is different from inorganic sodium salt generated by neutralizing with inorganic acid, wherein the inorganic sodium salt can generally seriously reduce the mechanical property of plastic products, but the former has the property of a surfactant, and some of the sodium salt can increase the compatibility of red mud particles and resin, and plays a certain role in improving the property of the plastic products. It also has an internal lubricating action, thereby improving the processability of the resin.

In addition, the long-chain organic acid can react with transition metal oxides in the red mud to form the transition metal salt or complex with the long-chain organic group, and the polar end of the transition metal salt or complex has stronger affinity with the red mud particles; the alkane and ester are used as non-polar or weak-polar end and have better affinity with resin, so the products have the function of reducing the interfacial energy of the red mud and the resin, thereby greatly improving the dispersibility and the fluidity of the red mud in the resin melt and improving and obviously improving the performance of the resin product.

The transition metal salt has stronger effect of absorbing ultraviolet radiation, thereby increasing the light stability of the resin product.

Compared with light calcium carbonate, the red mud treated by the invention not only can be used as a filling material of resin products, but also has the function of certain functional filling materials.

The invention has the beneficial effects that:

1. the invention provides grafted wax as a red mud treatment agent, and the treated red mud can completely replace the existing filler processed by resin. The red mud treated by the red mud treating agent is used for processing resin or plastics, and the processing performance of the red mud is obviously improved.

2. After the treating agent is used for treating the red mud, the application value of the red mud can be greatly improved, the treating agent can be used as a filler for toughening, lubricating and reinforcing plastics, the problem of pollution of the red mud to the environment can be greatly solved, and the cost of plastic products can be reduced.

3, the addition amount of the red mud treated by the method in polyethylene, polypropylene and polyvinyl chloride is more than 33 percent and can reach 60 percent at most.

5. According to the invention, the waste residue red mud is used for plastic products after being treated, and the method has important significance for comprehensive utilization of the red mud.

Detailed Description

The present invention is further illustrated by, but is not limited to, the following specific examples.

The raw materials used in the examples are all conventional raw materials and commercial products unless otherwise specified.

Example 1 Fischer-Tropsch wax grafting of maleic acid monobutyl ester

Adding Fischer-Tropsch wax (model CHF100 ℃) of 50kg, maleic acid monobutyl ester of 5kg and dicumyl peroxide of 0.05kg into a reactor, stirring and heating, reacting for 20-40min at the temperature of 165-175 ℃, and granulating by a granulator. The graft ratio of the resulting graft was 2.5%. Acid number 3.5g KOH/100g resin.

Example 2

50kg of petroleum wax (No. 58 wax) was used in place of the Fischer-Tropsch wax of example 1, and the procedure was repeated except for using the same wax as in example 1. The graft ratio of the graft wax was 2.6%, and the acid value was 3.4g KOH/100g resin.

Example 3

50kg of polyethylene wax (average molecular weight 2000-3000) was used in place of the petroleum wax of example 1, and the rest was the same as in example 1. The graft ratio of the resulting graft was 2.2%. Acid number 3.4g KOH/100g resin.

Example 4

The same procedure as in example 1 was repeated except that 50kg of polypropylene wax (number average molecular weight: 2000) was used in place of the petroleum wax of example 1. The graft ratio of the resulting graft was 2.6%. Acid number 3.4g KOH/100g resin.

Example 5

Adding Fischer-Tropsch wax (model CHF100 ℃) of 50kg, maleic acid monobutyl ester of 2kg, diethylene glycol bismaleic acid monoester of 2kg, trihydroxypropane tricaleic acid monoester of 1kg and dicumyl peroxide of 0.01kg into a reactor, stirring and heating, reacting for 20-40min at the temperature of 165-175 ℃, and granulating by a granulator. The graft ratio of the resulting graft was 2.6%. Acid number 3.5g KOH/100g resin.

Example 6

16kg of the grafted Fischer-Tropsch wax of example 1 was heated to 60-90 ℃ and about 4kg of water was added in portions with stirring, the ingredients were stirred rapidly to form an emulsified liquid, and the temperature was maintained at 80-90 ℃ for future use.

Examples 7 to 10

16kg of the grafted petroleum wax of example 2, 16kg of the grafted polyethylene wax of example 3, 16kg of the grafted polypropylene wax of example 4 and 16kg of the grafted Fischer-Tropsch wax of example 5 were heated to 60 to 90 ℃ respectively, and about 4kg of water was added in portions with stirring to rapidly stir the ingredients into an emulsified liquid for later use.

Example 11

30000g of red mud (the red mud with high water content can be centrifuged to remove part of alkali-containing water) with water content of 45% and free NaOH content of 0.5% (calculated by dry red mud), the red mud is placed in a reactor, stirred at room temperature, slowly added with 510.0g, 868.0g and 1241.8g of the treating agents (calculated by water-free treating agents) prepared in example 6, and after sufficient reaction, centrifuged, dehydrated, dried, crushed and sieved by a 800-mesh sieve to obtain treated red mud (calculated by dry red mud and water-free treating agents) with the addition of 3%, 5% and 7% of grafted Fischer-Tropsch wax treating agent, and the corresponding pH values are 8.5, 8.0 and 7.6.

Examples 12 to 15

The procedure of example 6 was repeated except that the treating agent obtained in example 6 was replaced with the grafted petroleum wax aqueous suspension emulsion obtained in example 7, the grafted polyethylene wax aqueous suspension emulsion obtained in example 8, the grafted polypropylene wax aqueous suspension emulsion obtained in example 9, and the grafted fischer-tropsch wax aqueous suspension emulsion obtained in example 10. Respectively obtaining grafted petroleum wax, grafted polyethylene wax, grafted polypropylene wax and mixed monomer grafted Fischer-Tropsch wax treated red mud with the addition of the treating agent of 3%, 5% and 7%.

Example 16

10kg of the dried red mud treated in example 11 was added with 20kg of powdered polyethylene (7042 powder), and the mixture was pelletized by extrusion in a twin-screw extruder. And (3) extruding at 175-210 ℃ to obtain resin particles, and performing injection molding on the obtained resin particles to obtain the standard part.

Example 17

5000g of the dried red mud treated in example 11 was added with 10000g of powdery polypropylene (F401) and extruded and pelletized in a twin-screw extruder. And (3) extruding at 175-205 ℃ to obtain resin particles, and performing injection molding on the obtained resin particles to obtain the standard part.

Example 18

5000g of the dried red mud treated in example 11 was added with 10000g of powdered polyvinyl chloride (SG-5), and according to the usual processing formula of polyvinyl chloride, 6% of stabilizer, 2% of stearic acid and 1% of paraffin were added. Extruding and granulating in a double-screw extruder. Extruding at 195-220 ℃ to obtain resin particles, and performing injection molding on the obtained resin particles to obtain the standard part.

Comparative example 1

As shown in example 16, except that: the same amount of light calcium carbonate was used as filler for polyethylene.

Comparative example 2

As shown in example 16, except that: untreated red mud was used as a filler for polyethylene.

Comparative example 3

As shown in example 17, except that: the same amount of light calcium carbonate is used as the filler of polypropylene.

Comparative example 4

As shown in example 17, except that: untreated red mud was used as a filler for polypropylene.

Comparative example 5

As shown in example 18, except that: the same amount of light calcium carbonate is used as the filler of polyvinyl chloride.

Comparative example 6

As shown in example 19, except that: the untreated red mud is used as the filler of powdery polyvinyl chloride.

Comparative example 7

Red mud was treated with unmodified fischer-tropsch wax as a red mud treatment agent as described in example 1, as a filler for polyethylene.

Test example 1

The product performance of example 16 and comparative examples 1-2 were tested and the results are shown in table 1:

TABLE 1

The treating agent accounts for the proportion of the red mud, and the treating agent and the red mud are calculated on a dry basis

From the data in Table 1 above, it can be seen that the Melt Index (MI) is significantly increased by replacing precipitated calcium carbonate with the same proportion of treated red mud, as compared to the conventional polyethylene processing with precipitated calcium carbonate, indicating that the grafted wax of the present invention has significant internal lubrication in the resin melt. Compared with the same amount of light calcium carbonate, the addition of the same amount of untreated red mud has slightly higher melt index. The polyethylene added with the red mud treated with the grafted wax of the invention (mass ratio 2:1) has a significantly increased melt index compared to the same amount of untreated red mud, and the melt index increases slightly with the addition of the treating agent.

From the data in Table 1, it can be seen that the mechanical properties of the red mud treated by adding polyethylene are slightly increased compared with those of the red mud treated by adding the same amount of light calcium carbonate. The increase of the impact strength is obvious, which shows that the red mud treated by the invention has a certain reinforcing effect.

As can be seen from Table 1, the Melt Index (MI), impact resistance and elongation of polyethylene prepared by using the Fischer-Tropsch wax treated red mud after grafting modification as a filler are all obviously improved compared with those of the Fischer-Tropsch wax without grafting.

Test example 2

The product performance of example 17 and comparative examples 3-4 were tested and the results are shown in table 2:

TABLE 2

As can be seen from the test data in Table 2, the addition of untreated red mud, and the addition of the same proportion of precipitated calcium carbonate, has a Melt Index (MI) close to that of the untreated red mud. The treated red mud replaces light calcium carbonate, and the melt index is obviously increased. The treating agent of the present invention is demonstrated to have a significant internal lubricating effect in the resin melt. This is similar to the case of polyethylene-added treated red mud. This is significant for the processing of the resin or for the extrusion process for the production of articles.

It can also be seen from the data in table 2 above that the impact resistance of the red mud treated by adding polypropylene is significantly increased (which is more significant to the performance of hard polypropylene products) compared with that of the red mud treated by adding the same amount of light calcium carbonate, and the other mechanical properties are slightly increased or close to those of the red mud treated by adding polypropylene. The data in Table 2 show that the red mud treated by the method not only can be used as a filler to replace light calcium carbonate, but also has certain functions of toughening and internal lubrication.

Test example 3

The product performance of example 18 and comparative examples 5-6 were tested and the results are shown in table 3:

TABLE 3

From the data in Table 3 above, it can be seen that the mechanical properties of the untreated red mud added to polyvinyl chloride are close to or slightly improved compared to the same amount of precipitated calcium carbonate. Compared with the addition of light calcium carbonate, the addition of the treated red mud has the advantages that the impact resistance mechanical property and the elongation at break are obviously improved. The other performances are close to or slightly improved.

The polyvinyl chloride added with the treated red mud has better fluidity during melt extrusion than when light calcium carbonate is added. The processing performance is obviously improved.

Claims

1. The red mud treating agent based on the grafted wax is characterized in that the treating agent is a branched chain carboxyl-containing graft modified wax.

2. The red mud treatment agent based on grafted wax according to claim 1, wherein the graft ratio of the branched carboxyl-containing graft-modified wax is 1.0-8.0%, and the acid value is 10-80g KOH/100g of the graft-modified wax.

3. The red mud treatment agent according to claim 1, wherein the branched chain carboxyl group-containing graft-modified wax is obtained by graft copolymerization of a wax with an unsaturated acid or an unsaturated acid derivative.

4. The red mud treatment agent based on grafted wax according to claim 3, wherein the wax is petroleum wax, Fischer-Tropsch wax, polyethylene wax or/and polypropylene wax.

5. The red mud treatment agent based on grafted wax according to claim 3, wherein the unsaturated acid is butenedioic acid, acrylic acid or/and methacrylic acid;

6. The method for preparing the red mud treatment agent based on grafted wax according to claim 1, comprising the following steps:

7. The use of the red mud treatment agent of claim 1 for treating red mud.

8. A method for treating red mud, which comprises using the red mud treating agent of claim 1, comprises the following steps:

adding a red mud treatment agent into water, heating, stirring, dispersing and emulsifying, and then uniformly adding the red mud treatment agent into the water-containing red mud to be treated; after the reaction is sufficient, centrifugally dewatering, drying, crushing and sieving to obtain the treated red mud;

preferably, the heating temperature is 60-90 ℃, and the mixture is sieved by a 800-1000-mesh sieve;

preferably, the addition amount of the red mud treatment agent is 6-25% of the mass of the water-containing red mud; the mass content of the hydrous red mud water is 30-50%.

9. The red mud masterbatch is prepared by adding resin into the red mud treated by the red mud treatment agent of claim 1 and performing melt extrusion, wherein the mass content of the red mud in the red mud masterbatch is 50-90%.

10. The red mud masterbatch of claim 9, wherein the resin is polyethylene, polypropylene or polyvinyl chloride.