Process for the preparation of a thermoplastic resin modifier and its use

Abstract

This invention discloses a method for preparing and applying a thermoplastic resin modifier. By designing a special core-shell structure, this invention first adds acidic functional monomers to the shell monomers, which are then neutralized to form carboxylate salts that act as emulsifiers. This significantly reduces the amount of emulsifier used, thus improving the yellowing problem during application. After the shell is formed, the core layer is swollen into the shell, forming a more complete core-shell structure. This results in the modifier possessing superior impact resistance and processability while maintaining excellent optical properties.

Description

Technical Field

[0001] This invention relates to an impact modifier having a rubber phase, and more particularly to a method for preparing and applying a thermoplastic resin modifier. Background Technology

[0002] PMMA resin, short for polymethyl methacrylate, commonly known as plexiglass or acrylic, is a very important transparent polymer material among plastics. It boasts advantages such as high transparency, high gloss, and excellent weather resistance, making it widely used in construction, electronics, and automotive industries. However, PMMA also has significant drawbacks: it is brittle and notch-sensitive, with relatively low impact strength, limiting its applications. A common modification method is to add impact-resistant modifiers with a rubber phase, such as the emulsion polymerization PMMA toughening agent provided in patent CN113004453B.

[0003] Common powdering processes for PMMA modifiers produced by emulsion polymerization include spray drying and coagulation. Spray drying uses steam heating to evaporate water from the emulsion, yielding the modifier powder. Coagulation involves demulsifying the emulsion with flocculants and then centrifuging and drying it. The former has the advantages of being simple and producing no industrial wastewater, making it more widely applicable. However, through continuous research, the inventors have discovered that PMMA modifier powder produced by spray drying is prone to yellowing during subsequent mixing processes, affecting its optical properties. Compared to PMMA modifier powder produced by coagulation, it is more difficult to guarantee its application effectiveness.

[0004] In-depth research revealed that the main reason for the yellowing problem is that the spray process leaves emulsifiers used in the emulsion polymerization method in the modifier powder. In the subsequent PMMA mixing process, the emulsifiers decompose due to heat, causing the PMMA to yellow and affecting its optical properties.

[0005] Therefore, based on how to reduce the amount of emulsifier added when preparing modifiers by emulsion polymerization, so as to make it more suitable for spray powdering and ensure the high transparency of PMMA, this invention proposes a new solution. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for preparing and applying a thermoplastic resin modifier. This invention utilizes a specially designed core-shell structure. First, acidic functional monomers are added to the shell monomers, which are then neutralized to form carboxylate salts that act as emulsifiers. This significantly reduces the amount of emulsifier used, thus improving the yellowing problem during application. After the shell is formed, the core layer is swollen into the shell, creating a more complete core-shell structure. This results in a modifier that, while maintaining excellent optical properties, also exhibits superior impact resistance and processability.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a thermoplastic resin modifier includes the following preparation process:

[0009] 1) Prepare shell preemulsion I and core monomer solution II according to the weight proportions;

[0010] Shell pre-emulsion I:

[0011] 500-700 parts of hard monomer, preferably 550-650 parts.

[0012] 10-80 parts of soft monomer, preferably 20-70 parts.

[0013] 120-180 parts of acid-based functional monomers, preferably 130-170 parts.

[0014] Chain transfer agent 5-11 parts, preferably 6-10 parts,

[0015] Emulsifier 0.5-5 parts, preferably 1-4 parts,

[0016] 120-220 parts water, preferably 130-200 parts.

[0017] Core layer monomer solution II:

[0018] The soft monomer content is 600-700 parts, preferably 610-680 parts;

[0019] 100-200 parts of hard monomer, preferably 120-190 parts;

[0020] Crosslinking monomer 0.5-5 parts, preferably 1-3 parts;

[0021] 2) Prepare the initiator solution and divide it into two portions, one as the bottom initiator and the other as the dropwise initiator;

[0022] 3) Using water as the base solution, heat the reactor to 80-90℃; add the bottom initiator all at once, mix well, then add shell pre-emulsion I and the initiator dropwise to carry out the shell polymerization reaction; after the reaction is complete, add the neutralizing agent dropwise and keep warm;

[0023] 4) Cool the reactor to 40-60℃, add core layer monomer solution II dropwise, followed by the accelerator, oxidant, and reducing agent; cool and discharge the material.

[0024] 5) The emulsion is powdered using a spray process to obtain the modifier.

[0025] In some embodiments, the hard monomer is one or both of styrene and methyl methacrylate;

[0026] Preferably, the soft monomer is one or more selected from isooctyl acrylate, butyl acrylate, ethyl acrylate, and methyl acrylate;

[0027] Preferably, the acid functional monomer is one or more of acrylic acid and methacrylic acid;

[0028] Preferably, the crosslinking monomer is one or more of ethylene glycol dimethacrylate, butanediol dimethacrylate, and divinylbenzene.

[0029] In some embodiments, the chain transfer agent is one or both of dodecyl mercaptan and n-octyl mercaptan;

[0030] Preferably, the emulsifier is one or two of disodium dodecyl diphenyl ether sulfonate and sodium dodecylbenzene sulfonate. The above types of emulsifiers have the characteristics of strong thermal stability. By selecting such emulsifiers, the yellowing phenomenon caused by the residue of traditional anionic emulsifiers (such as sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether sulfate emulsifiers) can be further avoided.

[0031] In some embodiments, the initiator is selected from potassium persulfate and / or sodium persulfate;

[0032] Preferably, the neutralizing agent is KOH and / or NaOH;

[0033] Preferably, the accelerator is a compound of ferrous sulfate and EDTA, and more preferably a compound with a mass ratio of 1:(1-3).

[0034] Preferably, the oxidant is one or both of tert-butyl hydroperoxide (TBHP) and cumene hydroperoxide;

[0035] Preferably, the reducing agent is one or more of sodium bisulfite, sodium formaldehyde sulfoxylate, and sodium metabisulfite.

[0036] In some implementations, in step 2), the mass ratio of the bottom initiator to the dropwise initiator is 1:(1-3);

[0037] Preferably, the total amount of initiator used in step 2) is 0.5-1.5 parts, more preferably 0.6-1.3 parts;

[0038] Preferably, the initiator solution has a mass concentration of 3-6 wt%.

[0039] In some implementations, in step 3), the addition time of the shell preemulsion I and the drop initiator is 1-3 hours;

[0040] Preferably, the neutralizing agent is added over a period of 1-20 minutes, and the heat preservation time is 10-30 minutes.

[0041] In some implementations, in step 4), the core layer monomer solution II is added over a period of 2-5 hours.

[0042] In some embodiments, the amount of neutralizing agent added is such that the pH of the neutralized emulsion is 7-9;

[0043] Preferably, the amount of the accelerator is 0.02-0.2 parts, more preferably 0.05-0.1 parts;

[0044] Preferably, the amount of the oxidant is 4-10 parts, more preferably 6-9 parts;

[0045] Preferably, the amount of the reducing agent is 3-8 parts, more preferably 5-7 parts;

[0046] Preferably, the amount of water used as the base coat in step 3) is 1200-2000 parts, more preferably 1300-1800 parts.

[0047] In some implementations, the spray process specifically involves spray drying the emulsion using a pressure spray dryer.

[0048] The present invention also provides an application of the thermoplastic resin modifier prepared by the method described above as a toughening modifier for thermoplastic resins, and in particular as a toughening modifier for PMMA resins.

[0049] The modifier prepared by this invention has a significantly reduced emulsifier dosage, which can fundamentally solve the yellowing phenomenon caused by emulsifier decomposition when applied to the processing of thermoplastic resins such as PMMA, and ensure the excellent optical properties, impact resistance, processability, etc. of the resin. Detailed Implementation

[0050] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0051] Unless otherwise specified, the raw materials used in the following embodiments and comparative examples of this invention were obtained from commercial sources.

[0052] The specific embodiments of this invention mainly involve the following testing methods:

[0053] Optical properties: PMMA resin was pressed into 2mm tablets on a tablet press and its optical properties were tested on a photometer and haze meter according to the ASTM D-1003 test method.

[0054] Mechanical properties: PMMA resin was made into standard impact specimens with a thickness of 4 mm according to ASTM D256. After cutting a V-shaped notch on the specimens with a cutting machine, the notched impact strength of the cantilever beam was determined.

[0055] Yellowing performance: PMMA resin is pressed into 3mm tablets on a tablet press, and the yellowing value and b value are tested on a yellowing meter according to the method in GB / T39822.

[0056]

Example 1

[0057] The modifier was prepared according to the following method:

[0058] 1) Prepare shell preemulsion I and core monomer solution II;

[0059] Shell pre-emulsion I: 600g methyl methacrylate, 40g methyl acrylate, 160g methacrylic acid, 6g n-dodecyl mercaptan, 1.2g sodium dodecylbenzenesulfonate, and 150g water.

[0060] Core layer monomer solution II: 640g butyl acrylate, 160 parts styrene, 1.6g ethylene glycol dimethacrylate.

[0061] 2) Weigh 0.3g of sodium persulfate and dissolve it in 5g of deionized water to prepare a bottom initiator solution; weigh 0.9g of sodium persulfate and dissolve it in 15g of deionized water to prepare a dropwise initiator solution;

[0062] 3) Using 1700g of water as the base solution, heat the reactor to 85℃; add the bottom initiator all at once, mix well, then add shell pre-emulsion I and the initiator dropwise to carry out the shell polymerization reaction; the dropwise addition takes 3 hours. After the dropwise addition is complete, immediately add 30wt% sodium hydroxide until the pH = 8, completing the dropwise addition in 10 minutes, and keep warm for 20 minutes;

[0063] 4) Cool the reactor to 50°C and add core layer monomer solution II dropwise over 3 hours; then add the accelerator, oxidant, and reductant; cool and discharge the product; the accelerator is prepared by dissolving 0.06g EDTA and 0.02g ferrous sulfate in 2g water; the oxidant is prepared by dissolving 9g TBHP in 20g water; and the reductant is prepared by dissolving 6.5g sodium formaldehyde sulfoxylate in 20g water.

[0064] 5) The emulsion is spray-dried using a pressure spray dryer to obtain the modifier.

[0065]

Examples 2-6

[0066] Referring to the process method in Example 1, the conditions were adjusted as shown in Table 1 to prepare the modifiers in Examples 2-6 respectively.

[0067] Table 1

[0068]

[0069]

[0070]

[0071] Comparative Example 1

[0072] 1) Prepare shell preemulsion I and core monomer solution II;

[0073] Core layer monomer solution I: 300g deionized water, 4g sodium dodecylbenzenesulfonate, 160g styrene, 640g butyl acrylate, 1.6g ethylene glycol dimethacrylate, and stirred thoroughly.

[0074] Shell pre-emulsion II: 300g deionized water, 7g sodium dodecylbenzenesulfonate, 760g methyl methacrylate, 40g methyl acrylate and 5g n-dodecyl mercaptan were prepared in pre-emulsification tank 1 and stirred thoroughly.

[0075] 2) Weigh 0.3g of sodium persulfate and dissolve it in 5g of deionized water to prepare a bottom initiator solution; weigh 1.0g of sodium persulfate and dissolve it in 15g of deionized water to prepare a dropwise initiator solution;

[0076] 3) Using 1300g of water as the base solution, heat the reactor to 85℃; add the bottom initiator all at once, mix thoroughly, then add core layer preemulsion I and the initiator dropwise to carry out the core layer polymerization reaction; the dropwise addition lasts for 3 hours. After the dropwise addition is complete, keep the temperature for 1 hour; then add shell layer preemulsion II and the initiator dropwise to carry out the shell layer polymerization reaction, the dropwise addition lasts for 3 hours.

[0077] 4) After the addition is complete, cool the reaction vessel to 40°C to obtain the emulsion;

[0078] 5) Weigh 1000g of the obtained emulsion into a reaction flask and maintain the temperature at 60℃. Add the flocculant solution (prepared from 15g magnesium sulfate and 1600g diluent water) dropwise to the flask over 1 hour. After the addition is complete, raise the temperature to 85℃ and maintain it for 1 hour. Then, lower the temperature to 50℃. Centrifuge and dry the resulting turbid liquid to obtain the modifier powder.

[0079] Comparative Example 2

[0080] 1) Prepare shell preemulsion I and core monomer solution II;

[0081] Core layer monomer solution I: 300g deionized water, 4g sodium dodecylbenzenesulfonate, 160g styrene, 640g butyl acrylate, 1.6g ethylene glycol dimethacrylate, and stirred thoroughly.

[0082] Shell pre-emulsion II: 300g deionized water, 7g sodium dodecylbenzenesulfonate, 760g methyl methacrylate, 40g methyl acrylate and 5g n-dodecyl mercaptan were prepared in pre-emulsification tank 1 and stirred thoroughly.

[0083] 2) Weigh 0.3g of sodium persulfate and dissolve it in 5g of deionized water to prepare a bottom initiator solution; weigh 1.0g of sodium persulfate and dissolve it in 15g of deionized water to prepare a dropwise initiator solution;

[0084] 3) Using 1300g of water as the base solution, heat the reactor to 85℃; add the bottom initiator all at once, mix thoroughly, then add core layer preemulsion I and the initiator dropwise to carry out the core layer polymerization reaction; the dropwise addition lasts for 3 hours. After the dropwise addition is complete, keep the temperature for 1 hour; then add shell layer preemulsion II and the initiator dropwise to carry out the shell layer polymerization reaction, the dropwise addition lasts for 3 hours.

[0085] 4) After the addition is complete, cool the reactor to 40°C;

[0086] 5) The emulsion is spray-dried using a pressure spray dryer to obtain modifier powder.

[0087] PMMA resin was modified with the modifiers provided in each example and comparative example (modification methods are as follows), and the performance tests of the obtained modified resins were performed as shown in Table 2.

[0088] The modifier and PMMA resin (Wanhua HD04) were mixed and granulated in a Thermo-Jakke twin-roll mill in Germany at a processing temperature of 220°C for 5 minutes to obtain the modified PMMA resin.

[0089] Table 2

[0090]

[0091] As can be seen from the test results in Table 2, the modified resin obtained after toughening PMMA resin with the modifier powder provided in Examples 1-6 of this invention has the advantages of good optical properties, high impact strength, and good resistance to yellowing. Comparative Examples 1 and 2 prepared the modifiers using the traditional core-shell emulsion polymerization process. Their application to PMMA resin modification had varying degrees of impact on the product's optical properties and yellowing resistance. In particular, Comparative Example 2, which used spray drying to produce powder based on the traditional core-shell emulsion polymerization process, severely affected the haze and yellowing resistance of the PMMA resin.

[0092] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a thermoplastic resin modifier, characterized in that, The preparation process includes the following: 1) Prepare shell preemulsion I and core monomer solution II according to the weight proportions; Shell pre-emulsion I: 500-700 parts of hard monomers 10-80 parts of soft monomer, 120-180 parts of acid-based functional monomers Chain transfer agent 5-11 parts, Emulsifier 0.5-5 parts, 120-220 parts water Core layer monomer solution II: 600-700 parts of soft monomers 100-200 parts of hard monomer, Crosslinking monomer 0.5-5 parts, 2) Prepare the initiator solution and divide it into two portions, one as the bottom initiator and the other as the dropwise initiator; 3) Using water as the base solution, heat the reactor to 80-90℃; add the bottom initiator all at once, mix well, then add shell pre-emulsion I and the initiator dropwise to carry out the shell polymerization reaction; after the reaction is complete, add the neutralizing agent dropwise and keep warm; 4) Cool the reactor to 40-60℃, add core layer monomer solution II dropwise, followed by the accelerator, oxidant, and reducing agent; cool and discharge the material. 5) The emulsion is powdered using a spray process to obtain the modifier; The hard monomer is one or both of styrene and methyl methacrylate; The soft monomer is one or more of isooctyl acrylate, butyl acrylate, ethyl acrylate, and methyl acrylate; The acid functional monomer is one or more of acrylic acid and methacrylic acid; The crosslinking monomer is one or more of ethylene glycol dimethacrylate, butanediol dimethacrylate, and divinylbenzene.

2. The method for preparing the thermoplastic resin modifier according to claim 1, characterized in that, Step 1) Prepare shell preemulsion I and core monomer solution II according to the weight proportions; Shell pre-emulsion I: 550-650 parts of hard monomer, 20-70 parts of soft monomer, 130-170 parts of acid-based functional monomers 6-10 parts of chain transfer agent, 1-4 parts emulsifier 130-200 parts water Core layer monomer solution II: 610-680 parts of soft monomer; 120-190 parts of hard monomer; Crosslinking monomer 1-3 parts.

3. The method for preparing the thermoplastic resin modifier according to claim 1, characterized in that, The chain transfer agent is one or both of dodecyl mercaptan and n-octyl mercaptan.

4. The method for preparing the thermoplastic resin modifier according to claim 3, characterized in that, The emulsifier is one or both of sodium dodecyl diphenyl ether sulfonate and sodium dodecyl benzene sulfonate.

5. The method for preparing the thermoplastic resin modifier according to any one of claims 1-4, characterized in that, The initiator is selected from potassium persulfate and / or sodium persulfate.

6. The method for preparing the thermoplastic resin modifier according to claim 5, characterized in that, The neutralizing agent is KOH and / or NaOH.

7. The method for preparing the thermoplastic resin modifier according to claim 5, characterized in that, The accelerator is a compound of ferrous sulfate and EDTA.

8. The method for preparing the thermoplastic resin modifier according to claim 7, characterized in that, The accelerator is a compound of ferrous sulfate and EDTA in a mass ratio of 1:(1-3).

9. The method for preparing the thermoplastic resin modifier according to claim 5, characterized in that, The oxidant is one or both of tert-butyl hydroperoxide and cumene hydroperoxide.

10. The method for preparing the thermoplastic resin modifier according to claim 5, characterized in that, The reducing agent is one or more of sodium bisulfite, sodium formaldehyde sulfoxylate, and sodium metabisulfite.

11. The method for preparing the thermoplastic resin modifier according to any one of claims 1-4, characterized in that, In step 2), the mass ratio of the bottom initiator to the dropwise initiator is 1:(1-3).

12. The method for preparing the thermoplastic resin modifier according to claim 11, characterized in that, The total amount of initiator used in 2) is 0.5-1.5 parts.

13. The method for preparing the thermoplastic resin modifier according to claim 12, characterized in that, The total amount of initiator used in 2) is 0.6-1.3 parts.

14. The method for preparing the thermoplastic resin modifier according to claim 11, characterized in that, The initiator solution has a mass concentration of 3-6 wt%.

15. The method for preparing the thermoplastic resin modifier according to any one of claims 1-4, characterized in that, In step 3), the addition time of the shell preemulsion I and the drop initiator is 1-3 hours.

16. The method for preparing the thermoplastic resin modifier according to claim 15, characterized in that, In step 3), the neutralizing agent is added over a period of 1-20 minutes and kept warm for 10-30 minutes.

17. The method for preparing the thermoplastic resin modifier according to any one of claims 1-4, characterized in that, In step 4), the core layer monomer solution II is added over a period of 2-5 hours.

18. The method for preparing the thermoplastic resin modifier according to any one of claims 1-4, characterized in that, The amount of neutralizing agent added is such that the pH of the neutralized emulsion is 7-9.

19. The method for preparing the thermoplastic resin modifier according to claim 18, characterized in that, The amount of the accelerator used is 0.02-0.2 parts.

20. The method for preparing the thermoplastic resin modifier according to claim 19, characterized in that, The amount of the accelerator used is 0.05-0.1 parts.

21. The method for preparing the thermoplastic resin modifier according to claim 18, characterized in that, The amount of the oxidant used is 4-10 parts.

22. The method for preparing the thermoplastic resin modifier according to claim 21, characterized in that, The amount of the oxidant used is 6-9 parts.

23. The method for preparing the thermoplastic resin modifier according to claim 18, characterized in that, The amount of the reducing agent used is 3-8 parts.

24. The method for preparing the thermoplastic resin modifier according to claim 23, characterized in that, The amount of the reducing agent used is 5-7 parts.

25. The method for preparing the thermoplastic resin modifier according to any one of claims 1-4, characterized in that, The spray process specifically involves spray-drying the emulsion using a pressure spray dryer.

26. The use of a thermoplastic resin modifier prepared by the method of any one of claims 1-25 as a toughening modifier for thermoplastic resins.

27. The use of a thermoplastic resin modifier prepared by the method of any one of claims 1-25 as a toughening modifier for PMMA resin.

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