CN116332805A - Process for preparing beta-naphthalenesulfonic acid formaldehyde condensate - Google Patents

Abstract

The invention discloses a preparation method of β-naphthalenesulfonic acid formaldehyde condensate, wherein when naphthalenesulfonic acid and formaldehyde are condensed to produce naphthalenesulfonic acid formaldehyde condensate, β-naphthalenesulfonic acid is controlled by sulfonation azeotropy The purity of ɑ-naphthalenesulfonic acid is hydrolyzed to adjust the acidity of the condensation reaction system, and the reflux ratio of the condensation process is adjusted to control the molar ratio of the reaction materials; the liquid alkali buffer improves the alkali resistance stability of the dispersant. The invention avoids the problem of producing a large amount of waste acid and waste gas in the process, and the prepared β-naphthalenesulfonic acid formaldehyde condensate not only has good dispersion effect, strong alkali resistance and stability, but also can be directly added to the dye as a dye additive without increasing The foaming property of the dyeing liquid increases the viscosity of the dyeing liquid, making it difficult to dye through, etc., and has no adverse effect on the dyeing process.

Description

The preparation method of β-naphthalenesulfonic acid formaldehyde condensate

technical field

The invention belongs to a preparation method of a dye dispersant, in particular to a preparation method of a β-naphthalenesulfonic acid formaldehyde condensate.

Background technique

Naphthalenesulfonic acid formaldehyde condensate is a class of anionic surfactants with excellent performance, used in water reducers and dyes

Wide range of applications in the industry. It has good dispersibility for metal oxides, clay, organic or inorganic pigments and dyes, and can also be used as a water reducing agent. In recent years, naphthalenesulfonic acid formaldehyde condensate has been widely used as dispersant for disperse dyes. By controlling the reaction conditions to make the degree of condensation appropriate, it is of great benefit to improve the application of the diffusing agent naphthalenesulfonic acid formaldehyde condensate.

In the prior art, the β-naphthalenesulfonic acid formaldehyde condensate is synthesized in four steps of sulfonation, hydrolysis, condensation, and neutralization using concentrated sulfuric acid, industrial naphthalene, and formaldehyde as raw materials, but in the process of sulfonation with concentrated sulfuric acid, as As the reaction proceeds, the concentration of concentrated sulfuric acid decreases, and the rate of reaction decreases almost to a halt. Therefore, industrially, a high proportion of sulfuric acid is used to promote the sulfonation reaction, resulting in an excessive amount of sulfuric acid, and a large amount of waste acid is treated with calcium hydroxide to introduce calcium After ionization, it is necessary to increase the desulfurization and decalcification process. And use oleum as sulfonating agent because the dehydration ability of sulfonating agent is too strong, can cause excessive sulfonation, produce more double sulfonated by-products, also reduce the yield of β-naphthalenesulfonic acid. Using sulfur trioxide as a sulfonating agent has higher requirements on production equipment. Naphthalenesulfonic acid formaldehyde condensate is not a single compound, but a mixture of products with different condensation degrees. The degree of condensation is mainly affected by the ratio of naphthylaldehyde in the condensation process, the temperature and time of the reaction, and the acidity. The traditional process continuously adjusts the molar ratio of naphthylaldehyde added to increase the degree of condensation of the product. The utilization rate of raw materials is low, and the degree of condensation is difficult to stabilize control.

Contents of the invention

The purpose of the invention is to provide a preparation method of β-naphthalenesulfonic acid formaldehyde condensate with good dispersion effect and strong alkali resistance stability. Its production steps are as follows:

(1) Sulfonation: Add 125-135 parts of naphthalene or industrial naphthalene to the reactor, heat up to 75-80°C, add 4-5 parts of cellulose-based super absorbent resin, start stirring, and then add under vacuum at 300-600mmHg 125-130 parts of sulfonating agent, then slowly raise the temperature to 155-165°C, keep the reaction at the temperature for 2.5-3.5h, and the gas generated by the reaction is absorbed by the scrubber;

(2) Naphthalene blowing: Add 15-20 parts of purified water with a temperature not lower than 50°C to the reactor, control the temperature of the reactor to 135-145°C, keep the temperature for 8-10 minutes, and The steps are repeated 3 times, each interval is 8-10 minutes, to hydrolyze the ɑ-naphthalenesulfonic acid, the hydrolyzed naphthalene overflows with the water vapor, and after being condensed by the condenser, it is filtered and recovered, and the remaining liquid in the reaction kettle is used as the reaction liquid.

(3) Condensation: transfer the reaction solution into a sealed high-pressure reactor with condensing reflux, the pressure of the high-pressure reactor is 0.55-0.75MPa, start stirring, and then slowly add 47-50 parts of 36%-38% Formaldehyde aqueous solution, control the reflux ratio, after the dropwise addition of the formaldehyde aqueous solution, the temperature in the sealed high-pressure reactor is raised to 105-110°C, and the reaction is kept at the temperature for 3.5-4.5h, and then 80-86 parts of To purify water, transfer all the materials in the above-mentioned sealed high-pressure reaction kettle to the neutralization kettle; the speed of adding the formaldehyde aqueous solution is controlled within 30 minutes.

(4) Neutralization: add 195-212 parts of liquid alkali buffer in the above neutralization kettle, after adding alkali, filter to obtain naphthalenesulfonic acid formaldehyde condensate solution;

(5) Drying: The naphthalenesulfonic acid formaldehyde condensate solution is pumped to a pressure spray drying tower for spray drying to obtain the product.

Further, in the step (1), the sulfonating agent is chlorosulfonic acid, 98% concentrated sulfuric acid and xylene, and the weight percentage of the components of the sulfonating agent is: chlorosulfonic acid: 98% concentrated sulfuric acid :xylene for 194-202:1:45-55.

Further, in the step (1), after adding the sulfonating agent, the slow temperature rise rate does not exceed 1°C per minute.

Further, in the step (3), the reflux ratio is 4:1-1:6, and the preferred reflux ratio is 1:1-1:1.2. In this state, the unreacted formaldehyde can be recycled to the greatest extent, forming The average condensation degree of the naphthalenesulfonic acid formaldehyde condensate is the highest.

Further, in the step (4), the liquid alkali buffer is ammonia water, vinylmethyldimethoxysilane, glycerin, trimethylglycine, and sodium silicate, and the weight of the liquid alkali buffer is The percentages are: Vinylmethyldimethoxysilane: Glycerin: Ammonia: Trimethylglycine: Sodium Silicate 3-7: 5-11: 1: 3-4: 15-22.

The beneficial effects of the present invention are as follows:

(1) Low-temperature sulfonation is kinetically controlled, and the main product is α-naphthalenesulfonic acid. High-temperature sulfonation is thermodynamically controlled, and the main product is β-naphthalenesulfonic acid. During the sulfonation process, sulfonating agents are added to high-temperature molten naphthalene , to reduce the by-product α-naphthalenesulfonic acid produced by low-temperature sulfonation during the heating process, and at the same time, the reactants at this stage are all liquid, which is conducive to the uniform mixing of the reactants, making the reaction more complete and improving the purity of the product.

(2) The present invention uses chlorosulfonic acid as a sulfonating agent, which can be directly added to the sulfonation reaction, while avoiding the difficult problem of sulfur trioxide tail gas produced by using oleum; the gas produced is absorbed by the scrubber, and the waste gas is recovered The utilization operation is simple, and the waste gas treatment cost is low; compared with the traditional process, using sulfuric acid as a sulfonating agent, the concentration of sulfuric acid is reduced after the reaction, the reaction rate is reduced, and the amount of waste acid produced is difficult to handle. The sulfonating agent used in the present invention can Control the stable progress of the reaction, thereby improving the reaction efficiency.

(3) Among the sulfonating agents used, the water produced by the concentrated sulfuric acid as the initiator and catalyst will hydrolyze naphthalenesulfonic acid, resulting in many by-products of the sulfonation reaction, low purity of the final product, and decreased dispersibility. The plain-based superabsorbent resin can control the system to proceed in an anhydrous environment, reducing the occurrence of side reactions. At the same time, the cellulose-based superabsorbent resin can effectively cover the surface of dye molecules, further inhibiting the association of dye molecules, and improving the dispersion performance of the product.

(4) The present invention reduces the escape of formaldehyde by performing condensation reaction in a sealed high-pressure reactor, and stabilizes the material ratio of reactants in the condensation process by controlling the reflux ratio of the condensation reflux device, thereby controlling the average condensation degree of the polymer.

(5) The present invention obtains the naphthalenesulfonic acid formaldehyde condensate with a high degree of condensation by controlling the material ratio of the reactants and the acidity of the reaction. The stronger the adsorption force of dye molecules, the less the association between dye molecules, and the better the dispersion effect.

(6) The waste acid produced by the present invention is very little, does not need to be treated with calcium hydroxide, reduces the introduction of calcium ions, and reduces the desulfurization and decalcification treatment process. However, because the acidic compounds in the whole system are unstable, the conventional medium It is difficult to control the pH range of the product with reagents, and the cellulose-based superabsorbent resin added in the sulfonation process can improve the dispersibility of the product, but it will increase the viscosity of the dye and make it difficult to dye through. In the liquid caustic buffer used in the present invention, sodium silicate can utilize the water that condensation reaction produces, and the free base that produces after hydrolysis can neutralize β-naphthalenesulfonic acid formaldehyde condensate, and silicic acid participates in the regulation of solution pH, has reduced Responding to the cost and the workload of the process, the buffer can stably control the pH of the system, realize the synergistic effect of the alkali resistance of the dye added to the product, and at the same time solve the problem of increased viscosity of the dye caused by the cellulose-based superabsorbent resin, which is difficult to dye through The problem is that the final product can be directly added to the dye as a dye additive, without increasing the foaming property of the dye solution, making the dye solution more viscous, difficult to dye through, etc., and has no adverse effects on the dyeing process.

Detailed ways

Below in conjunction with embodiment the present invention will be described in further detail, but protection scope of the present invention is not limited thereto:

Example 1

This embodiment includes the following steps:

(1) Sulfonation: Add 130kg of naphthalene or industrial naphthalene to the reactor, heat up to 78°C, add 4kg of cellulose-based superabsorbent resin, start stirring, and then add 128L of chlorosulfonic acid: 98% concentrated sulfuric acid under 450mmHg vacuum : The sulfonating agent whose xylene weight percentage is 198:1:50, then slowly heats up to 160°C, the speed of heating up is 0.9°C/min, keeps the reaction at the temperature for 3h, and the gas generated by the reaction passes through the scrubber absorb;

(2) Naphthalene blowing: the reaction kettle was cooled to 140°C, 18L of purified water at 50°C was added, and kept at the temperature for 9 minutes, and the steps were repeated 3 times with an interval of 9 minutes each time to hydrolyze the ɑ-naphthalenesulfonic acid, The hydrolyzed naphthalene overflows with water vapor, and after being condensed by a condenser, it is recovered by filtration, and the remaining liquid in the reaction kettle is used as a reaction liquid.

(3) Condensation: the reaction solution is transferred into a sealed high-pressure reactor with condensing reflux, the pressure of the high-pressure reactor is 0.65MPa, the stirring is started, and the drop rate of 37% formaldehyde solution is set to 1.6kg/min. After adding 0.5 hours, the reflux ratio is controlled to be 1:1.2. After the dropwise addition of the formaldehyde aqueous solution is completed, the temperature in the sealed autoclave is raised to 108° C., and the reaction is kept at the temperature for 4 hours, and then 83 L of purified water is added. All the materials in the above-mentioned sealed high-pressure reaction kettle are transferred into the neutralization kettle.

(4) Neutralization: Add 203L vinylmethyldimethoxysilane: glycerin: ammonia water: trimethylglycine: sodium silicate with a weight percentage of 5:8:1:4:19 in the above neutralization kettle Alkali buffer, after the alkali is added, filter to obtain the naphthalenesulfonic acid formaldehyde condensate solution;

(5) Drying: The naphthalenesulfonic acid formaldehyde condensate solution is pumped to a pressure spray drying tower for spray drying to obtain the product.

Example 2

This embodiment includes the following steps:

(1) Sulfonation: Add 125kg of naphthalene or industrial naphthalene to the reactor, heat up to 75°C, add 4kg of cellulose-based superabsorbent resin, start stirring, and then add 130L of chlorosulfonic acid: 98% concentrated sulfuric acid under 300mmHg vacuum : The sulfonating agent whose xylene weight percentage is 192:1:55, then slowly heats up to 165°C, the speed of heating up is 1.1°C/min, keeps the reaction at the temperature for 3.5h, and the gas generated by the reaction is washed absorber;

(2) Naphthalene blowing: the reaction kettle was cooled down to 135°C, 20L of purified water at 40°C was added, and kept at the temperature for 10 minutes, the steps were repeated 3 times with an interval of 10 minutes each time to hydrolyze the ɑ-naphthalenesulfonic acid, The hydrolyzed naphthalene overflows with water vapor, and after being condensed by a condenser, it is recovered by filtration, and the remaining liquid in the reaction kettle is used as a reaction liquid.

(3) Condensation: the reaction liquid is transferred into a sealed high-pressure reactor with condensing reflux, the pressure of the high-pressure reactor is 0.75MPa, the stirring is started, and the drop rate of 37% formaldehyde aqueous solution is set to 0.8kg/min. Add for 1 hour, and control the reflux ratio to 4:1. After the formaldehyde aqueous solution is added dropwise, the temperature in the sealed autoclave is raised to 110° C., and the reaction is kept at the temperature for 3.5 hours, and then 80 L of purified water is added. Transfer all the materials in the above-mentioned sealed autoclave to the neutralization autoclave.

(4) Neutralization: Add 212L vinylmethyldimethoxysilane: glycerin: ammonia water: trimethylglycine: sodium silicate with a weight percentage of 2:4:1:4:22 in the above neutralization kettle Alkali buffer, after the alkali is added, filter to obtain the naphthalenesulfonic acid formaldehyde condensate solution;

(5) Drying: The naphthalenesulfonic acid formaldehyde condensate solution is pumped to a pressure spray drying tower for spray drying to obtain the product.

Example 3

This embodiment includes the following steps:

(1) Sulfonation: Add 135kg of naphthalene or industrial naphthalene to the reactor, heat up to 80°C, add 5kg of cellulose-based superabsorbent resin, start stirring, and then add 125L of chlorosulfonic acid: 98% concentrated sulfuric acid under 600mmHg vacuum : The sulfonating agent whose xylene weight percentage is 205:1:44, then slowly heats up to 155°C, the speed of heating up is 1.0°C/min, keeps the reaction at the temperature for 2.5h, and the gas generated by the reaction is washed absorber;

(2) Naphthalene blowing: the reaction kettle was cooled down to 145°C, 15L of purified water at 60°C was added, and kept at the temperature for 8 minutes, and the steps were repeated 3 times with an interval of 8 minutes each time to hydrolyze the ɑ-naphthalenesulfonic acid, The hydrolyzed naphthalene overflows with water vapor, and after being condensed by a condenser, it is recovered by filtration, and the remaining liquid in the reaction kettle is used as a reaction liquid.

(3) Condensation: the reaction solution is transferred into a sealed high-pressure reactor with condensing reflux, the pressure of the high-pressure reactor is 0.55MPa, the stirring is started, and the drop rate of 37% formaldehyde aqueous solution is set to 3.2kg/min. After adding 0.25 hours, the reflux ratio is controlled to be 1:6. After the dropwise addition of the formaldehyde aqueous solution is completed, the temperature in the sealed autoclave is raised to 105° C., and the reaction is kept at the temperature for 4.5 hours, and then 86 L of purified water is added. All the materials in the above-mentioned sealed high-pressure reaction kettle are transferred into the neutralization kettle; the speed of adding the formaldehyde aqueous solution is controlled within 30 minutes.

(4) Neutralization: Add 195L of vinylmethyldimethoxysilane: glycerin: ammonia water: trimethylglycine: sodium silicate with a weight percentage of 8:12:1:3:10 in the above neutralization kettle Alkali buffer, after the alkali is added, filter to obtain the naphthalenesulfonic acid formaldehyde condensate solution;

(5) Drying: The naphthalenesulfonic acid formaldehyde condensate solution is pumped to a pressure spray drying tower for spray drying to obtain the product.

Comparative example 1

Add 130kg of naphthalene or industrial naphthalene to the reaction kettle, add 4kg of cellulose-based superabsorbent resin, start stirring, and then add 128L of chlorosulfonic acid under 450mmHg vacuum: 98% concentrated sulfuric acid: xylene The weight percentage is 198:1:50 The sulfonating agent is slowly heated to 160°C at a rate of 0.8°C/min, and the reaction is kept at the temperature for 3 hours, and the gas generated by the reaction is absorbed by the scrubber;

Other steps are with embodiment 1

Comparative example 2

Add 130kg of naphthalene or industrial naphthalene into the reaction kettle, heat up to 78°C, start stirring, and then add 128L of chlorosulfonic acid: 98% concentrated sulfuric acid: sulfonating agent with a weight percentage of xylene of 198:1:50 under a vacuum of 450mmHg , and then slowly warming up to 160°C, the speed of heating up is 1.3°C/min, and the temperature is kept at the temperature for 3h, and the gas generated by the reaction is absorbed by the scrubber;

Other steps are with embodiment 1

Comparative example 3

(1) Sulfonation: Add 130kg of naphthalene or industrial naphthalene to the reactor, heat up to 78°C, add 4kg of cellulose-based superabsorbent resin, start stirring, and then add 128L of chlorosulfonic acid: 98% concentrated sulfuric acid under 450mmHg vacuum : the sulfonating agent whose weight percentage of xylene is 198:1:50, then slowly heat up to 140°C, the speed of temperature rise is 0.6°C/min, keep warm at the temperature for 3h, and the gas generated by the reaction passes through the scrubber absorb;

(2) Blowing naphthalene: add 18L of purified water at 50°C to the reaction kettle, and keep it warm at the temperature for 9 minutes. The water vapor overflows, and after being condensed by the condenser, it is filtered and recovered, and the remaining liquid in the reaction kettle is used as the reaction liquid.

Other steps are with embodiment 1

Comparative example 4

Step is with embodiment 1

The sulfonating agent is chlorosulfonic acid, 98% concentrated sulfuric acid and xylene, and the weight percentage of the components of the sulfonating agent is: chlorosulfonic acid: 98% concentrated sulfuric acid: xylene=155:1:50.

Comparative example 5

Step is with embodiment 1

The sulfonating agent is chlorosulfonic acid, 98% concentrated sulfuric acid and xylene, and the weight percentage of the components of the sulfonating agent is: chlorosulfonic acid: 98% concentrated sulfuric acid: xylene=255:1:50.

Comparative example 6

Step is with embodiment 1

The sulfonating agent is chlorosulfonic acid and 98% concentrated sulfuric acid, and the weight percentage of the components of the sulfonating agent is: chlorosulfonic acid: 98% concentrated sulfuric acid=198:1.

Comparative example 7

(1) Sulfonation: Add 130kg of naphthalene or industrial naphthalene to the reactor, heat up to 78°C, add 4kg of cellulose-based superabsorbent resin, start stirring, and then add 128L of chlorosulfonic acid: 98% concentrated sulfuric acid under 450mmHg vacuum : The sulfonating agent whose xylene weight percentage is 198:1:50, then slowly heats up to 160°C, the speed of heating up is 0.9°C/min, keeps the reaction at the temperature for 3h, and the gas generated by the reaction passes through the scrubber absorb;

(2) Naphthalene blowing: the reaction kettle was cooled to 140°C, 54L of purified water at 50°C was added, and kept at the temperature for 27 minutes to hydrolyze the ɑ-naphthalenesulfonic acid, and the hydrolyzed naphthalene overflowed with water vapor and was condensed by the condenser Afterwards, it is recovered by filtration, and the remaining liquid in the reaction kettle is used as the reaction liquid.

Other steps are with embodiment 1

Comparative example 8

The control condensation process reflux ratio is 5:1 other steps are the same as embodiment 1

Comparative example 9

The control condensation process reflux ratio is 1:7, and other steps are with embodiment 1

Comparative example 10

Sodium hydroxide is added into the neutralization tank to adjust the pH to 7.5. After adding the alkali, filter to obtain a naphthalenesulfonic acid formaldehyde condensate solution;

Other steps are with embodiment 1

Comparative example 10

The liquid alkali buffer is ammonia water and sodium silicate, and the weight percentage of the liquid alkali buffer is: sodium silicate:ammonia water=19:1.

Other steps are with embodiment 1

Comparative example 11

The liquid alkali buffering agent is ammonia water, vinylmethyldimethoxysilane, glycerol, and sodium silicate, and the component weight percent of the liquid alkali buffering agent is: vinylmethyldimethoxysilane: glycerol : ammonia water: sodium silicate=5:8:1:19.

Other steps are with embodiment 1

Comparative example 12

The liquid alkali buffer is ammonia water, glycerol, trimethylglycine, and sodium silicate, and the component weight percent of the liquid alkali buffer is: glycerol: ammonia water: trimethylglycine: sodium silicate=8:1 :4:19.

Other steps are with embodiment 1

Comparative example 13

The liquid alkali buffer is ammonia water, vinylmethyldimethoxysilane, trimethylglycine, and sodium silicate, and the component weight percent of the liquid alkali buffer is: vinylmethyldimethoxy Silane: ammonia water: trimethylglycine: sodium silicate=5:1:4:19.

Other steps are with embodiment 1

Performance Testing

(1) The present invention separates each component of naphthalenesulfonic acid formaldehyde condensate with high performance liquid chromatography gradient leaching method, and measures the mass number of each component in naphthalenesulfonic acid formaldehyde condensate with liquid chromatography, thereby determines each component The degree of condensation, and then calculate the average degree of condensation of naphthalenesulfonic acid formaldehyde condensate:

(2) Dispersion performance is determined by GB/T 5550-2016 Surfactant Dispersion Test Method, in which the standard product of dispersibility is dispersant NNO model 36290-04-7 of Wuhan Huaxiang Kejie Biotechnology Co., Ltd.;

(3) Reactive Brilliant Blue KN-R was dry blended to 100% strength with naphthalenesulfonic acid formaldehyde condensate, and the alkali resistance synergistic effect of additives on reactive dyes was determined by cold pad batch alkali resistance test method (C method) , observe the time when the precipitates start to precipitate.

The specific results are shown in Table 1 below, wherein, in Comparative Example 1, excessive sulfonation produced too much disulfonic acid, and the data was abnormal.

Table 1

Average degree of condensation Dispersion power (for standard product), % Alkali resistance stability (time for solid precipitation), min Example 1 2.02 109 >90 Example 2 1.98 105 >90 Example 3 1.96 103 >90 Comparative example 1 —— —— —— Comparative example 2 1.76 81 31 Comparative example 3 1.73 88 67 Comparative example 4 1.61 64 63 Comparative example 5 1.34 41 61 Comparative example 6 1.71 84 65 Comparative example 7 1.77 89 71 Comparative example 8 1.69 67 67 Comparative example 9 1.63 65 65 Comparative example 10 2.01 89 19 Comparative example 11 1.98 101 53 Comparative example 12 1.99 93 42 Comparative example 13 2.02 107 37

As can be seen from Table 1, the average condensation degree of the naphthalenesulfonic acid formaldehyde polymer prepared by the embodiments of the present application 1-3 is stable, the dispersion effect is excellent, and the alkali resistance stability is strong, and the naphthalenesulfonic acid formaldehyde polymer prepared by the inventive method It can be directly added to the dye as a dye additive, without increasing the foaming property of the dye liquor, increasing the viscosity of the dye liquor, making it difficult to dye through, etc., and has no adverse effect on the dyeing process.

Claims (6)

1. A preparation method of naphthalene sulfonic acid formaldehyde condensate is characterized by comprising the following steps: the production steps are as follows:

(1) Sulfonation: adding 125-135 parts of naphthalene or industrial naphthalene into a reaction kettle, heating to 75-80 ℃, adding 4-5 parts of cellulose-based super absorbent resin, starting stirring, adding 125-130 parts of sulfonating agent under 300-600mmHg vacuum, slowly heating to 155-165 ℃, preserving heat at the temperature for 2.5-3.5 hours, and absorbing gas generated by the reaction by a scrubber;

(2) Blowing naphthalene: adding 15-20 parts of purified water with the temperature not lower than 50 ℃ into the reaction kettle, controlling the temperature of the reaction kettle to be 135-145 ℃, preserving the temperature for 8-10min at the temperature, repeating the steps for 3 times, and separating 8-10min each time to hydrolyze alpha-naphthalene sulfonic acid, wherein hydrolyzed naphthalene overflows along with water vapor, and filtering and recycling after condensing by a condenser, wherein the residual liquid in the reaction kettle is used as reaction liquid;

(3) Condensation: transferring the reaction solution into a sealed high-pressure reaction kettle with condensation reflux, wherein the pressure of the high-pressure reaction kettle is 0.55-0.75MPa, stirring is started, then 47-50 parts of 36-38% formaldehyde aqueous solution is slowly added, the reflux ratio is controlled, after the formaldehyde aqueous solution is added dropwise, the temperature in the sealed high-pressure reaction kettle is raised to 105-110 ℃, the temperature is kept for 3.5-4.5 hours for reaction, then 80-86 parts of purified water is added, and all materials in the sealed high-pressure reaction kettle are transferred into a neutralization kettle; the dripping speed of the formaldehyde aqueous solution is controlled to be within 30 minutes;

(4) And (3) neutralization: adding 195-212 parts of liquid alkali buffer into the neutralization kettle, and filtering after alkali addition is finished to obtain naphthalene sulfonic acid formaldehyde condensate solution;

(5) And (3) drying: and (3) conveying the naphthalene sulfonic acid formaldehyde condensate solution to a pressure spray drying tower through a pump, and performing spray drying to obtain a product.

2. The process for producing a naphthalene sulfonic acid formaldehyde condensate as claimed in claim 1, wherein: the sulfonating agent in the step (1) is chlorosulfonic acid, 98% concentrated sulfuric acid and dimethylbenzene, and the sulfonating agent comprises the following components in percentage by weight: chlorosulfonic acid: 98% concentrated sulfuric acid: xylene is 194-202:1:45-55.

3. The process for producing a naphthalene sulfonic acid formaldehyde condensate as claimed in claim 1, wherein: the slow temperature rise rate in the step (1) is not more than 1 ℃/min.

4. The process for producing a naphthalene sulfonic acid formaldehyde condensate as claimed in claim 1, wherein: the reflux ratio in the step (3) is 4:1-1:6.

5. A process for the preparation of naphthalene sulfonic acid formaldehyde condensate as claimed in claim 1 or 4, wherein: the reflux ratio is 1:1-1:1.2.

6. The process for producing a naphthalene sulfonic acid formaldehyde condensate as claimed in claim 1, wherein: in the step (4), the liquid alkali buffer is ammonia water, vinylmethyldimethoxy silane, glycerol, trimethylglycine and sodium silicate, and the liquid alkali buffer comprises the following components in percentage by weight: vinyl methyl dimethoxy silane: glycerol: ammonia water: trimethylglycine: sodium silicate 3-7:5-11:1:3-4:15-22.