A method for preparing HCPE resin for environmentally friendly and weather-resistant adhesive

Abstract

The invention discloses a method for preparing an environmentally friendly and weather-resistant HCPE resin for an adhesive, and belongs to the technical field of high chlorinated polyethylene resin. The preparation method comprises the following steps: chlorination and post-treatment. For the chlorination, the polyethylene resin and water are mixed, stirring is started, an initiator and a dispersant are added, vacuum is drawn in a sealed environment, and chlorine is introduced after the temperature is raised to 70 DEG C to carry out a chlorination reaction. For the post-treatment, after the introduction of chlorine in the chlorination is completed, the temperature is lowered to 78-82 DEG C, filtered, washed with a first portion of water, and then crushed, spray-washed with a second portion of water through a vacuum flat plate filter, and then heated to 83-87 DEG C, sodium carbonate is added for stirring, neutralized to a pH value of 6.8-7.2, and then centrifuged and dried. The preparation method of the invention can reduce the residual acid content in the prepared HCPE resin.

Description

Technical Field

[0001] The invention relates to the technical field of high chlorinated polyethylene resins, and in particular to a method for preparing an environmentally friendly and weather-resistant HCPE resin for an adhesive. Background Art

[0002] Highly chlorinated polyethylene resin for adhesive (HCPE resin for short) is a high molecular weight polymer made from polyethylene resin by deep chlorination. It has good solubility and compatibility and is soluble in solvents such as ethylene dichloride, cyclohexanone, and tetrahydrofuran. It is currently the most widely used resin raw material in domestic PVC adhesives. Adhesives prepared with HCPE resin usually use ethylene dichloride as the main solvent. They have the advantages of low cost and good bonding performance, and are widely used in the bonding field of domestic PVC pipes, fittings, and plates.

[0003] At present, PVC adhesives abroad are mainly made of chloroacetic acid resins, special CPVC resins, etc. as raw materials, and the solvent system usually uses ketones, esters, tetrahydrofuran and other complex solvents. Although chlorocarbon solvents such as dichloroethane are cheap, their use abroad is greatly restricted due to their potential harm to the environment and human health.

[0004] The production process of HCPE resin adopts the aqueous suspension method, and a large amount of hydrochloric acid will be produced during the chlorination substitution reaction. Although post-treatment processes such as water washing and neutralization can eliminate most of the hydrochloric acid in the material, there is still a trace amount of hydrochloric acid remaining inside the particles. The adhesive prepared by non-chlorinated hydrocarbon solvents such as ketones, esters, and tetrahydrofuran and HCPE resin will slowly react chemically due to the presence of residual acid, resulting in poor weather resistance of the product, easy discoloration after long-term storage or heating, and even gelation, which cannot meet the customer's requirement of no obvious discoloration after being stored in a 52°C oven for 1 month. This is also the main reason that restricts the promotion and development of HCPE resin in the foreign PVC adhesive market.

[0005] In the HCPE resin aqueous suspension production method, chlorine gas generates chlorine free radicals under the action of an initiator, and undergoes substitution reactions with the surface of the raw PE resin particles and into the interior of the particles through the pore structure. The hydrogen atoms on the molecular chain are replaced by chlorine atoms, generating hydrogen chloride and releasing heat. In this process, the weight of the resin particles gradually increases, eventually reaching about 3 times the original weight; the volume also gradually increases, showing significant expansion. Most of the hydrogen chloride produced by the chlorination substitution reaction dissolves into the water phase, and a small part remains inside the material particles. During the washing, neutralization and drying process after the chlorination reaction, most of the residual acid inside the material particles will gradually diffuse out from the inside through the pore structure of the particles, or directly neutralize into sodium chloride. However, during the chlorination and expansion process of the resin particles, part of the original pore structure is deformed and blocked, resulting in the difficulty of washing or neutralizing the hydrogen chloride generated by the substitution reaction inside some materials through the post-processing process.

[0006] In order to remove the residual acid in the PVC adhesive made from HCPE resin as raw material, the inventor tried to add alkaline substances to the PVC adhesive. However, since inorganic bases cannot be dissolved in organic solvents, not only can the problem of discoloration caused by the release of acid after the HCPE resin is dissolved in the adhesive solvent not be solved, but also the transparency of the adhesive will be significantly deteriorated; organic bases mostly contain organic substances such as N and P, which will directly react and discolor after entering the adhesive. Therefore, it is impossible to solve the problem of discoloration of the PVC adhesive caused by excessive residual acid in the HCPE resin by directly adding alkaline substances to the PVC adhesive.

[0007] In view of the above problems, the inventors have tried to adjust the chlorine gas introduction rate in the production of HCPE resin, increase the chlorine introduction rate in the high temperature section, thereby increasing the volume expansion multiple and specific surface area of ​​the HCPE resin, and forming a large number of void structures inside the HCPE resin, and then crushing it to make it easy for the residual acid blocked inside the HCPE resin to diffuse outward and be neutralized. However, in actual production, it is found that although increasing the chlorine introduction rate in the high temperature section can obtain HCPE resin with a high volume expansion multiple, it will cause adhesion problems. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention provides a method for preparing an environmentally friendly, weather-resistant HCPE resin for an adhesive, which can reduce the residual acid content in the prepared HCPE resin.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing an environmentally friendly, weather-resistant HCPE resin for adhesives, comprising the following steps: chlorination, post-treatment;

[0011] For the chlorination, the polyethylene resin and water are mixed, stirred, an initiator and a dispersant are added, and the mixture is evacuated in a sealed environment. After the temperature is raised to 70° C., chlorine gas is introduced to carry out a chlorination reaction;

[0012] In the chlorination, the molecular weight of the polyethylene resin is 90,000-120,000, the polyethylene resin with a particle size range of 0.074-0.154 mm accounts for more than 90%, and the melting range is 126-128°C;

[0013] In the chlorination, the ratio of polyethylene resin to water is 290-310kg:7.5-8.5m 3 ;

[0014] In the chlorination, the initiator is a combination of dodecanoyl peroxide and didecanoyl peroxide, wherein the usage ratio of dodecanoyl peroxide to didecanoyl peroxide is 1.9-2.1kg:2.8-3.2kg;

[0015] In the chlorination, the dispersant is sodium polymethacrylate;

[0016] In the chlorination, the usage ratio of polyethylene resin, initiator and dispersant is 290-310kg:4.7-5.3kg:9.5-10.5kg;

[0017] In the chlorination, the vacuum pressure after evacuation is -0.085MPa to -0.075MPa;

[0018] In the chlorination, the ratio of the amount of polyethylene resin to the total amount of chlorine is 290-310kg:1090-1210kg;

[0019] In the chlorination, the chlorination reaction is divided into six stages. The temperature of the first stage is 70-85°C, the amount of chlorine is 162-182kg, and the rate of chlorine is 4.9-5.1kg / min; the temperature of the second stage is 85-100°C, the amount of chlorine is 106-126kg, and the rate of chlorine is 4.9-5.1kg / min; the temperature of the third stage is 100-126°C, the amount of chlorine is 185-205kg, and the rate of chlorine is 4.4-4.6 kg / min; the temperature of the fourth stage reaction is 126-128℃, the chlorine flow rate is 427-447kg, and the chlorine flow rate is 3.4-3.6kg / min; the temperature of the fifth stage reaction is 128-131℃, the chlorine flow rate is 128-148kg, and the chlorine flow rate is 3.4-3.6kg / min; the temperature of the sixth stage reaction is 130.5-131.5℃, the chlorine flow rate is 82-102kg, and the chlorine flow rate is 2.4-2.6kg / min;

[0020] The post-treatment comprises cooling the mixture to 78-82° C. after the chlorination reaction is completed, filtering, washing with the first portion of water, and then crushing the mixture to obtain primary HCPE resin particles; spray-washing the primary HCPE resin particles with the second portion of water through a vacuum plate filter to obtain a slurry; heating the slurry to 83-87° C., adding sodium carbonate for stirring, neutralizing the slurry to a pH value of 6.8-7.2, and then centrifuging and drying the slurry to obtain a finished HCPE resin;

[0021] The ratio of the amount of the polyethylene resin in the chlorination to the first portion of water and the second portion of water in the post-treatment is 290-310 kg: 4.5-5.5 m 3 :11-13m 3 ;

[0022] In the post-treatment, the average particle size of the primary HCPE resin particles is 0.08-0.12 mm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The method for preparing an environmentally friendly, weather-resistant HCPE resin for an adhesive of the present invention comprises adjusting the chlorine gas introduction rate during the production of the HCPE resin, increasing the chlorine introduction rate in the high temperature stage, thereby increasing the volume expansion multiple and specific surface area of ​​the HCPE resin, forming a large number of void structures inside the HCPE resin, which is more conducive to the outward diffusion and neutralization of the residual acid blocked inside after crushing, thereby reducing the residual acid content, and dividing the chlorination reaction into six stages. By controlling the temperature of the first stage reaction to a relatively low temperature, specifically to 70-85° C., a shell with a relatively high chlorine content can be formed on the surface of the polyethylene resin, thereby preventing adhesion in the later stage; and then increasing the temperature of the second stage reaction to a relatively low temperature. The temperature of the reaction is controlled to 85-100°C, so that the chlorine free radicals can be uniformly chlorinated; the temperature of the third stage reaction is controlled to 100-126°C, and the chlorine flow rate is gradually increased; the temperature of the fourth stage reaction is controlled to 126-128°C, the chlorine flow rate is reduced, the inside of the resin is softened, the resin particles are rapidly expanded, and a large number of chlorine free radicals enter the inside of the resin for chlorination; the temperature of the fifth stage reaction is controlled to 128-131°C, and the temperature is further increased to further chlorinate the inside of the resin; finally, the temperature of the sixth stage reaction is controlled to 131°C to ensure uniform chlorination inside the resin; thereby obtaining a HCPE resin with uniform chlorination, high chlorine content, large volume expansion multiple, and no adhesion;

[0025] (2) The method for preparing an environmentally friendly and weather-resistant HCPE resin for an adhesive of the present invention has a chlorine content of 68.1%, an apparent density of 0.23 g / mL, and a residual chlorine (calculated as HCl) of 21 μg / g. The HCPE resin is dissolved in a mixed solvent consisting of 45% cyclohexanone, 35% tetrahydrofuran, and 20% ethyl acetate at a solid content of 10%. The appearance after dissolution is transparent and colorless, and the viscosity is 379 mPa·s. There is no color change when stored in an oven at 52° C. for 1 month. Therefore, the adhesive prepared by the HCPE resin prepared by the present invention has the advantages of good environmental protection and high weather resistance, and meets the relevant industry standards and the use requirements of domestic and foreign customers. DETAILED DESCRIPTION

[0026] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0027] Example 1

[0028] A method for preparing an environmentally friendly, weather-resistant HCPE resin for an adhesive, specifically comprising:

[0029] 1. Chlorination:

[0030] 300kg polyethylene resin, 8m3 Add water to the enamel reactor, start stirring, add 2kg initiator dodecyl peroxide, 3kg didecyl peroxide, 10kg dispersant sodium polymethacrylate, seal and evacuate to a vacuum pressure of -0.08MPa, heat to 70°C and start passing chlorine, then heat and pass chlorine to carry out chlorination reaction, control the total chlorine flow rate of the chlorination reaction to be 1150kg, the chlorination reaction is divided into six stages, the temperature, chlorine flow rate and chlorine flow rate of each stage are as follows:

[0031] The first stage of reaction: the temperature is 70-85℃, the chlorine flow rate is 172kg, and the chlorine flow rate is 5.0kg / min;

[0032] The second stage of reaction: the temperature is 85-100℃, the chlorine flow rate is 116kg, and the chlorine flow rate is 5.0kg / min;

[0033] The third stage of reaction: the temperature is 100-126℃, the chlorine flow rate is 195kg, and the chlorine flow rate is 4.5kg / min;

[0034] The fourth stage of reaction: the temperature is 126-128°C, the chlorine flow rate is 437kg, and the chlorine flow rate is 3.5kg / min;

[0035] The fifth stage of reaction: the temperature is 128-131°C, the amount of chlorine is 138kg, and the rate of chlorine is 3.5kg / min;

[0036] The sixth stage of reaction: the temperature is 131°C, the amount of chlorine is 92kg, and the rate of chlorine is 2.5kg / min;

[0037] The molecular weight of the polyethylene resin is 110,000, the particle size range of the polyethylene resin is 0.074-0.154 mm, accounting for 92%, and the melting range is 126-128°C;

[0038] 2. Post-processing:

[0039] After the chlorine gas is introduced, the temperature is lowered to 80°C, transferred to the water washing kettle, filtered and then 5m 3 The average particle size of the resin particles was 0.35 mm after sampling and drying. The particles were then ground into a titanium alloy slurry grinder to an average particle size of 0.1 mm. The particles were then repeatedly sprayed and washed with a vacuum flat filter for a total of 12 m 3 Water was added to obtain a slurry, which was then transferred into a neutralization kettle, heated to 85°C, 4.5 kg of sodium carbonate was added, stirred for 2 hours, neutralized to a pH value of 7, and then centrifuged and dried to obtain 811 kg of HCPE resin finished product.

[0040] The test results of the HCPE resin product obtained in this embodiment are as follows:

[0041]

[0042] Example 2

[0043] The changes are made on the basis of Example 1, and the changes are as follows:

[0044] In the second post-processing step, the titanium alloy slurry is not transferred to the pulverizer for pulverization, that is, the second post-processing step is changed to:

[0045] After the chlorine gas is introduced, the temperature is lowered to 80°C, transferred to the water washing kettle, filtered and then 5m 3 The average particle size of the resin particles was 0.35 mm after sampling and drying, and then the resin particles were repeatedly sprayed and washed by a vacuum flat filter for a total of 12 m 3 Water was added to obtain a slurry, which was then transferred to a neutralization kettle, heated to 85°C, 4.2 kg of sodium carbonate was added, stirred for 2 hours, neutralized to a pH value of 7, and then centrifuged and dried to obtain 857 kg of HCPE resin finished product.

[0046] The test results of the HCPE resin product obtained in this embodiment are as follows:

[0047]

[0048] It can be seen from the results of this example that due to the material loss during pulverization, the weight of the obtained HCPE resin product will increase due to the omission of pulverization. However, if pulverization is not performed, the residual acid in some gaps cannot be removed by alkali washing, resulting in a decrease in the amount of sodium carbonate and an increase in the residual acid content. Therefore, the hydrogen chloride content in the HCPE resin product obtained in this example is significantly higher than that in Example 1, and after being dissolved in the composite solvent and stored in an oven at 52°C for 1 month, there is obvious discoloration.

[0049] Example 3

[0050] The changes are made on the basis of Example 1, and the changes are as follows:

[0051] In the first chlorination step, the amount of chlorine passed through each stage of the chlorination reaction is changed, that is, each stage of the reaction in the first chlorination step is changed to:

[0052] The first stage of reaction: the temperature is 70-85℃, the chlorine flow rate is 210kg, and the chlorine flow rate is 5.0kg / min;

[0053] The second stage of reaction: the temperature is 85-100℃, the chlorine flow rate is 275kg, and the chlorine flow rate is 5.0kg / min;

[0054] The third stage of reaction: the temperature is 100-126℃, the chlorine flow rate is 233kg, and the chlorine flow rate is 4.5kg / min;

[0055] The fourth stage of reaction: the temperature is 126-128°C, the amount of chlorine is 183kg, and the rate of chlorine is 3.5kg / min;

[0056] The fifth stage of reaction: the temperature is 128-131°C, the chlorine flow rate is 180kg, and the chlorine flow rate is 3.5kg / min;

[0057] The sixth stage of reaction: the temperature is 131°C, the amount of chlorine is 69 kg, and the rate of chlorine is 2.5 kg / min;

[0058] In the second post-processing step, samples were taken before being transferred into the titanium alloy slurry crusher to test the average particle size, which was 0.21 mm, that is, the resin particle size was significantly smaller than that in Example 1.

[0059] The slurry was transferred into a neutralization kettle, heated to 85°C, sodium carbonate was added, stirred for 2 hours, and neutralized to a pH value of 7. A total of 4.3 kg of sodium carbonate was consumed, and 823 kg of HCPE resin products were finally obtained.

[0060] The test results of the HCPE resin product obtained in this embodiment are as follows:

[0061]

[0062] It can be seen from the results of this example that by changing the amount of chlorine passed in each stage of the reaction, the particle size of the resin after chlorination is reduced, which is not conducive to the removal of residual acid in the resin after crushing. Therefore, the hydrogen chloride content in the HCPE resin product obtained in this example is higher than that in Example 1, resulting in slight discoloration after being dissolved in the composite solvent and stored in an oven at 52° C. for 1 month.

[0063] Unless otherwise specified, all percentages used in the present invention are by mass.

[0064] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an environmentally friendly, weather-resistant HCPE resin for an adhesive, characterized in that: It consists of the following steps: chlorination, post-treatment; For the chlorination, the polyethylene resin and water are mixed, stirred, an initiator and a dispersant are added, and the mixture is evacuated in a sealed environment. After the temperature is raised to 70° C., chlorine gas is introduced to carry out a chlorination reaction; In the chlorination, the chlorination reaction is divided into six stages. The temperature of the first stage is 70-85°C, the amount of chlorine is 162-182kg, and the rate of chlorine is 4.9-5.1kg / min; the temperature of the second stage is 85-100°C, the amount of chlorine is 106-126kg, and the rate of chlorine is 4.9-5.1kg / min; the temperature of the third stage is 100-126°C, the amount of chlorine is 185-205kg, and the rate of chlorine is 4.4-4.6 kg / min; the temperature of the fourth stage reaction is 126-128℃, the chlorine flow rate is 427-447kg, and the chlorine flow rate is 3.4-3.6kg / min; the temperature of the fifth stage reaction is 128-131℃, the chlorine flow rate is 128-148kg, and the chlorine flow rate is 3.4-3.6kg / min; the temperature of the sixth stage reaction is 130.5-131.5℃, the chlorine flow rate is 82-102kg, and the chlorine flow rate is 2.4-2.6kg / min; In the chlorination, the ratio of the amount of polyethylene resin to the total amount of chlorine is 290-310kg:1090-1210kg; The post-treatment comprises cooling the mixture to 78-82° C. after the chlorination reaction is completed, filtering, washing with the first portion of water, and then crushing the mixture to obtain primary HCPE resin particles; spray-washing the primary HCPE resin particles with the second portion of water through a vacuum plate filter to obtain a slurry; heating the slurry to 83-87° C., adding sodium carbonate for stirring, neutralizing the slurry to a pH value of 6.8-7.2, and then centrifuging and drying the slurry to obtain a finished HCPE resin; In the post-treatment, the average particle size of the primary HCPE resin particles is 0.08-0.12 mm.

2. The method for preparing the environmentally friendly and weather-resistant HCPE resin for adhesives according to claim 1, characterized in that: In the chlorination, the molecular weight of the polyethylene resin is 90,000-120,000, the polyethylene resin with a particle size range of 0.074-0.154 mm accounts for more than 90%, and the melting range is 126-128°C.

3. The method for preparing the environmentally friendly and weather-resistant HCPE resin for adhesives according to claim 1, characterized in that: In the chlorination, the ratio of polyethylene resin to water is 290-310kg:7.5-8.5m 3 .

4. The method for preparing the environmentally friendly and weather-resistant HCPE resin for adhesives according to claim 1, characterized in that: In the chlorination, the initiator is a combination of dodecanoyl peroxide and didecanoyl peroxide, wherein the usage ratio of dodecanoyl peroxide to didecanoyl peroxide is 1.9-2.1kg:2.8-3.2kg.

5. The method for preparing the environmentally friendly and weather-resistant HCPE resin for adhesives according to claim 1, characterized in that: In the chlorination, the dispersant is sodium polymethacrylate.

6. The method for preparing the environmentally friendly and weather-resistant HCPE resin for adhesives according to claim 1, characterized in that: In the chlorination, the usage ratio of polyethylene resin, initiator and dispersant is 290-310kg:4.7-5.3kg:9.5-10.5kg.

7. The method for preparing the environmentally friendly and weather-resistant HCPE resin for adhesives according to claim 1, characterized in that: In the chlorination, the vacuum pressure after evacuation is -0.085 MPa to -0.075 MPa.

8. The method for preparing the environmentally friendly and weather-resistant HCPE resin for adhesives according to claim 1, characterized in that: The ratio of the amount of the polyethylene resin in the chlorination to the first portion of water and the second portion of water in the post-treatment is 290-310 kg: 4.5-5.5 m 3 :11-13m 3 .

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