Thermoplastic acrylate polymer with thermal degradation resistance and preparation method thereof

Abstract

The invention discloses a thermal degradation resistant thermoplastic acrylate polymer and a preparation method thereof. In the preparation process of the thermoplastic acrylate polymer, the low glass transition temperature of the thermoplastic acrylate polymer is realized by controlling the copolymerization proportion of the second monomer acrylate monomer, and the proportion of the small molecular weight component is controlled to be 0.5-1.5 wt% by adding the molecular chain stabilizer. Therefore, product defects caused by degradation of a small molecular weight part in a film stretching process are reduced, namely excellent high-temperature-resistant thermal degradation performance is realized. The thermoplastic acrylate copolymer resin has excellent high-temperature-resistant thermal degradation performance and lower glass transition temperature, does not influence the melt strength of the resin, and can be used for materials in the fields with high processing performance and processing temperature requirements of single-layer films, multi-layer films and multi-layer composite films and the like.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a thermoplastic acrylate copolymer with excellent heat degradation resistance and its preparation method. Background Technology

[0002] Thermoplastic acrylate copolymers are a class of thermoplastic polymers polymerized from copolymerizable monomers. Due to their unique thermoplastic properties, these polymers are widely used in the automotive, home appliance, cosmetic packaging, lighting, and film markets.

[0003] Thermoplastic resins have high requirements for processing technology in film applications. During the film making and stretching process, various defects are easily generated, such as surface bubbles and bubble patterns, poor thickness dimensional stability, poor mechanical properties, thermal stability, and optical properties, resulting in a large number of unqualified products and losses.

[0004] Current common technologies involve adding hindered phenolic antioxidants to resins to improve the heat resistance of materials by capturing free radicals generated during the degradation of thermoplastic acrylate copolymers at high temperatures. However, the manufacturing processes for films and film stretching typically involve high temperatures. Hindered phenolic antioxidants, while effective at high temperatures, are rapidly consumed, simultaneously generating small colored molecular groups. If not properly controlled, this can lead to severe yellowing problems. Therefore, in the film market, the amount of antioxidants added is generally very small, or even nonexistent.

[0005] The main cause of defects in the film manufacturing process is the depolymerization of molecular chains, which leads to the generation of a large amount of volatiles within the resin during processing. When the volatile content increases to a certain level, it causes blistering on the film surface at high temperatures, resulting in uneven resin flow, uneven film thickness, and even a decrease in the material's mechanical properties. Instability during the film stretching process also leads to a deterioration in the film's optical properties. Molecular chains with a molecular weight of less than 10,000 are the most easily degraded. However, the molecular weight distribution of free radical polymerization follows a normal distribution. There are currently no reported technical methods to further reduce the proportion of molecular chains with a molecular weight of less than 10,000 without changing the molecular weight. At the same time, there are no good technical methods to improve the thermal stability of small molecular chain segments.

[0006] JP6869642B2 mentions that a molecular weight distribution preferably below 2.8 is not a limitation. Controlling the molecular weight distribution within this range ensures the melt flowability of the acrylate copolymers mentioned in the patent. By making the molecular weight distribution below 3.0, the tensile strength of the acrylate copolymers can be improved, thus increasing melt flowability. However, it does not mention that an excessively wide molecular weight distribution will lead to an increased proportion of molecular weight segments below 10,000 in the product. These segments are more prone to degradation during processing, adversely affecting the produced film.

[0007] JP2006193650A mentions that phenolic antioxidants and sulfur-based antioxidants are effective in improving the heat aging resistance of acrylic rubber. However, this still pertains to the use and principle of external additives in capturing free radicals during long-term thermo-oxidative aging. It does not mention their effectiveness in improving the distribution of polymer molecular weight or reducing small molecule segments below 10,000.

[0008] CN217418588U mentions that by incorporating inorganic substances to form complex structures with oxygen atoms on the molecular chains of materials, a protective and isolating effect can be achieved, thereby improving the defects caused by thermal decomposition and the production of a series of small molecule degradation products. However, the incorporation of inorganic substances into acrylate optical films has a significant impact on the optical properties of the films. Summary of the Invention

[0009] This invention provides a thermoplastic acrylate polymer with excellent heat resistance and degradation resistance, and its preparation method. This invention reduces the high-temperature degradation of polymer molecular chains during the devolatilization process by adding a molecular chain stabilizer, and further weakens its continued decomposition by attaching sulfur atoms to the end groups of low molecular weight chain segments. This results in a product with excellent molecular weight distribution and heat resistance, without affecting the resin's base color and properties.

[0010] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0011] A thermoplastic acrylate polymer resistant to heat degradation, prepared from the following raw materials:

[0012] I. First comonomer: methacrylate monomer, 50-100 parts by weight, preferably 60-90 parts by weight;

[0013] II. Second comonomer: acrylate monomer, 1-50 parts by weight, preferably 10-40 parts by weight;

[0014] The glass transition temperature of the polymer is controlled at 60-90℃, and 0.00001-0.00015 parts by mass of molecular chain stabilizer are added to the polymer. The molecular weight distribution of the polymer is 1.7-1.9, and the proportion of small molecule polymers with a weight average molecular weight of less than 10,000 is controlled at 0.5-1.5 mol%. This is based on the polymer being 100%.

[0015] As a preferred embodiment of the present invention, the heat-resistant thermoplastic acrylate polymer has a weight-average molecular weight of 50,000-200,000, preferably 100,000-150,000.

[0016] As a preferred embodiment of the present invention, the thermoplastic acrylate polymer with heat resistance and degradation contains 1-50 wt% acrylate monomers, preferably 10-40 wt%, based on 100 wt% of all types of monomers participating in the main chain polymerization.

[0017] As a preferred embodiment of the present invention, the methacrylate monomer is selected from one or more of methyl methacrylate, ethyl methacrylate, and butyl methacrylate, preferably methyl methacrylate.

[0018] As a preferred embodiment of the present invention, the acrylate monomer is selected from one or more of methyl acrylate, ethyl acrylate, and butyl acrylate, preferably methyl acrylate and / or ethyl acrylate, and more preferably methyl acrylate.

[0019] As a preferred embodiment of the present invention, the molecular chain stabilizer is selected from one or more of dilauryl thiodipropionate, distearate thiodipropionate, di(tridecyl) thiodipropionate, dioctyl thiosuccinate, benzyl thiobenzoate, dimethyl dithiocarbonate, and tert-dodecyl mercaptan disulfide, preferably one or more of dilauryl thiodipropionate, distearate thiodipropionate, and tert-dodecyl mercaptan disulfide.

[0020] The polymerization process of the thermoplastic acrylate copolymer described in this invention can be any one of bulk polymerization, solution polymerization, or suspension polymerization. From the perspective of product performance and process matching, batch or continuous bulk polymerization is preferred, and continuous bulk polymerization is more preferred.

[0021] As a preferred embodiment, the method for preparing the heat-resistant thermoplastic acrylate polymer of the present invention includes the following steps:

[0022] S1: Ingredients:

[0023] Reaction solution A is prepared by mixing methacrylate monomers, acrylate monomers, initiators, and chain transfer agents;

[0024] The molecular chain stabilizer and the mold release agent are heated and melted to prepare auxiliary agent liquid A;

[0025] S2: Polymerization reaction:

[0026] Reaction solution A is subjected to polymerization to prepare slurry A; slurry A is subjected to polymerization to prepare slurry B; slurry B is mixed with auxiliary agent solution A and then subjected to polymerization to prepare slurry C.

[0027] S3: Extrusion devolatilization:

[0028] Slurry C is added to a devolatilizer, undergoes multi-stage devolatilization, and is then extruded through a die to obtain the product.

[0029] As a preferred embodiment of the present invention, the initiator in S1 is one or more of the following: benzoyl peroxide, tert-butyl peroxide-2-ethylhexanoate, tert-butyl peroxide-isobutyrate, tert-butyl peracetic acid, dicumyl peroxide, 1,1-bis-(tert-butylperoxide)-3,3,5-trimethylcyclohexane, tert-butyl peroxide-3,5,5-trimethylhexanoate, tert-butyl peroxide-benzoate, tert-butyl peroxide-isopropylbenzene, cumene hydroperoxide, and tert-butyl hydroperoxide; preferably tert-butyl peroxide-3,5,5-trimethylhexanoate and / or dicumyl peroxide, more preferably tert-butyl peroxide-3,5,5-trimethylhexanoate.

[0030] Preferably, the amount of initiator added in reaction solution A is 0.001-0.015 parts by mass per 100 parts by mass of monomer, and more preferably 0.005-0.009 parts by mass, wherein the monomer comprises methacrylate monomers and acrylate monomers.

[0031] Preferably, the chain transfer agent in S1 is one or more of n-butanethiol, tert-butanethiol, n-octanethiol, isooctanethiol, n-dodecylthiol, and tert-dodecylthiol, with n-octanethiol being the most preferred.

[0032] Preferably, the chain transfer agent is added at a ratio of 0.05-0.3 parts by weight per 100 parts by weight of monomer, more preferably 0.1-0.25 parts by weight, wherein the monomer comprises methacrylate monomers and acrylate monomers.

[0033] Preferably, the molecular chain stabilizer is added at a ratio of 0.0005-0.01 parts by mass per 100 parts by mass of slurry A, and more preferably 0.001-0.005 parts by mass.

[0034] Preferably, the release agent is one or more of alkyl alcohols or alkyl acids with 1-30 carbon atoms, more preferably one or more of alkyl alcohols or alkyl acids with 6-20 carbon atoms, and more preferably one or more of alkyl alcohols or alkyl acids with 14-18 carbon atoms; further preferably one or more of hexadecyl alcohol, octadecyl alcohol, hexadecyl acid, and octadecyl acid, with an addition ratio of 0.05-0.3 parts by weight per 100 parts by weight of slurry A, preferably 0.08-0.12 parts by weight.

[0035] As a preferred embodiment of the present invention, the reactor for preparing slurry A in S2 is a fully mixed-flow high-pressure reactor; the reaction temperature is controlled at 120-150℃; the reaction residence time is controlled at 2-5h; the resulting slurry A mainly contains a copolymer of methacrylate monomers and acrylate monomers, and also contains methacrylate monomers and acrylate monomers.

[0036] Preferably, the reactor for preparing slurry B or slurry C in S2 is a fully mixed-flow high-pressure reactor and / or a plug flow reactor, preferably a plug flow reactor. The reaction temperature for preparing slurry B or C is controlled at 150-190℃. The reaction residence time for preparing slurry B or C is controlled at 10-50 min. The resulting slurry C mainly contains copolymers of methacrylate monomers and acrylate monomers, and also contains methacrylate monomers, acrylate monomers, and molecular chain stabilizers.

[0037] Preferably, in S3, the devolatilizer can be a static devolatilizer and / or a screw extrusion devolatilizer, preferably a screw extrusion devolatilizer.

[0038] Preferably, the screw extruder devolatilizer is a multi-stage devolatilization extruder, controlling the devolatilization temperature at 230-260℃ and the vacuum degree at 2-20KPa, removing most of the methacrylate monomers and acrylate monomers. The resulting product contains ≤5ppm of molecular chain stabilizers, and the proportion of small molecule polymers with a weight average molecular weight below 10000 is 0.5-1.5wt%. The product has a molecular weight distribution of 1.7-1.9 and a glass transition temperature of 60-90℃.

[0039] The thermoplastic acrylate copolymers with heat resistance and degradation described in this invention are used in materials for single-layer films, multilayer films, and multilayer composite films, where high processing performance and processing temperature are required. Detailed Implementation

[0040] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0041] Unless otherwise specified, the raw materials and reagents used in the following embodiments of the present invention were all purchased from commercial sources. The main raw material information is shown in Table 1:

[0042] Table 1. Information on Main Raw Materials

[0043] Raw material name Other names or abbreviations level supplier Methyl methacrylate MMA Industrial grade Sinopharm Methyl acrylate MA Industrial grade Sinopharm Ethyl acrylate EA Industrial grade Sinopharm tert-butyl peroxide 3,5,5-trimethylhexanoate TBPMH Industrial grade Sinopharm n-Octamethrin NOM Industrial grade Chevron dilaurate thiodipropionate DLTP Industrial grade Lianlong Distearate of thiodipropionate DSTP Industrial grade Lianlong tert-dodecyl disulfide / Industrial grade Lianlong Octadecanol / Industrial grade Sinopec

[0044] The following are the methods for testing the structure and properties of polymers:

[0045] Molecular weight determination: Molecular weight was determined by gel electrophoresis (GPC) with tetrahydrofuran (THF) as the mobile phase and a parallax refractive index detector. Monodisperse PMMA was used as the standard sample. Instrument manufacturer: Agilent Technologies; Instrument model: 1260 Infinity; Test standard: GB / T 21863-2008.

[0046] YI value: Optical performance can be measured using a colorimeter, including total light transmittance, haze, and YI value. Instrument model: Hunterlab VIS; Test standards: Haze ISO 14782, transmittance ISO 13148.

[0047] Melt Flow Index Test: The MFR is determined using a melt flow indexer. Instrument manufacturer: GOTTFERT; Instrument model: MI 40; Test standard: ASTM D1238.

[0048] Residual monomer testing: Quantitative testing of residual components is performed using headspace gas chromatography. Pre-separation is required via dissolution-sedimentation pretreatment. The supernatant is then used for quantitative analysis via headspace sampler and gas chromatography. Instrument model: Agilent 6890N.

[0049] Glass transition temperature (Tg) test: The glass transition temperature of the polymer was tested by differential scanning calorimetry. Test instrument: Mettler-Toledo-DSC1.

[0050] Heat resistance test: The heat resistance residence time of the material in the barrel is tested by injection molding machine at 270℃ for 30 minutes. The material is then injected into a 3mm optical sheet to test the YI value and molecular weight.

[0051] Example 1

[0052] S1. Ingredients: Add 75kg of methyl methacrylate, 25kg of methyl acrylate, 8g of initiator tert-butyl peroxide 3,5,5-trimethylhexanoate (TBPMH), and 150g of n-octyl mercaptan (NOM) to mixing tank A to prepare reaction solution A; add 5g of dilauryl thiodipropionate and 100g of octadecyl alcohol to mixing tank B, maintaining the tank temperature at 90-110℃ for thorough melting and mixing to prepare auxiliary agent solution A;

[0053] S2. Polymerization reaction: Add reaction solution A to reactor A to carry out the polymerization reaction, control the polymerization temperature at 135℃ and the residence time at 2h to obtain slurry A; add the slurry to reactor B for the next polymerization reaction, control the polymerization temperature at 155℃ and the residence time at 0.5h to obtain slurry B; then add slurry B and auxiliary agent solution A to reactor C through a static mixer for the next polymerization reaction, control the reaction temperature at 190℃ and the residence time at 0.5h to obtain slurry C;

[0054] S3. Extrusion devolatilization: Add slurry C to the extrusion devolatilizer, control the devolatilization temperature at 250℃, the vacuum degree at 2.5KPa, and the residence time at 5min, and obtain the product through extrusion and granulation.

[0055] Example 2

[0056] S1. Ingredients: Add 75kg of methyl methacrylate, 25kg of methyl acrylate, 8g of initiator TBPMH, and 150g of n-octyl mercaptan to mixing tank A to prepare reaction solution A; add 3g of distearate thiodipropionate and 100g of octadecyl alcohol to mixing tank B, maintain the temperature inside the tank at 90-110℃ and fully melt and mix to prepare auxiliary agent solution A;

[0057] S2. Polymerization reaction: Add reaction solution A to reactor A to carry out the polymerization reaction, control the polymerization temperature at 135℃ and the residence time at 2h to obtain slurry A; add the slurry to reactor B for the next polymerization reaction, control the polymerization temperature at 155℃ and the residence time at 0.5h to obtain slurry B; then add slurry B and auxiliary agent solution A to reactor C through a static mixer for the next polymerization reaction, control the reaction temperature at 190℃ and the residence time at 0.5h to obtain slurry C;

[0058] S3. Extrusion devolatilization: Add slurry C to the extrusion devolatilizer, control the devolatilization temperature at 250℃, the vacuum degree at 2.5KPa, and the residence time at 5min, and obtain the product through extrusion and granulation.

[0059] Example 3

[0060] S1. Ingredients: Add 75kg of methyl methacrylate, 25kg of methyl acrylate, 8g of initiator TBPMH, and 150g of n-octyl mercaptan to mixing tank A to prepare reaction solution A; add 1g of tert-dodecyl mercaptan disulfide and 100g of octadecyl alcohol to mixing tank B, maintain the temperature inside the tank at 90-110℃ and fully melt and mix to prepare auxiliary agent solution A;

[0061] S2. Polymerization reaction: Add reaction solution A to reactor A to carry out the polymerization reaction, control the polymerization temperature at 135℃ and the residence time at 2h to obtain slurry A; add the slurry to reactor B for the next polymerization reaction, control the polymerization temperature at 155℃ and the residence time at 0.5h to obtain slurry B; then add slurry B and auxiliary agent solution A to reactor C through a static mixer for the next polymerization reaction, control the reaction temperature at 190℃ and the residence time at 0.5h to obtain slurry C;

[0062] S3. Extrusion devolatilization: Add slurry C to the extrusion devolatilizer, control the devolatilization temperature at 250℃, the vacuum degree at 2.5KPa, and the residence time at 5min, and obtain the product through extrusion and granulation.

[0063] Example 4

[0064] S1. Ingredients: Add 65kg of methyl methacrylate, 35kg of methyl acrylate, 8g of initiator TBPMH, and 140g of n-octyl mercaptan to mixing tank A to prepare reaction solution A; add 1g of tert-dodecyl mercaptan disulfide and 100g of octadecanol to mixing tank B, maintain the temperature inside the tank at 90-110℃ and fully melt and mix to prepare auxiliary agent solution A.

[0065] S2. Polymerization reaction: Add reaction solution A to reactor A to carry out the polymerization reaction, control the polymerization temperature at 135℃ and the residence time at 2h to obtain slurry A; add the slurry to reactor B for the next polymerization reaction, control the polymerization temperature at 155℃ and the residence time at 0.5h to obtain slurry B; then add slurry B and auxiliary agent solution A to reactor C through a static mixer for the next polymerization reaction, control the reaction temperature at 190℃ and the residence time at 0.5h to obtain slurry C;

[0066] S3. Extrusion devolatilization: Add slurry C to the extrusion devolatilizer, control the devolatilization temperature at 250℃, the vacuum degree at 2.5KPa, and the residence time at 5min, and obtain the product through extrusion and granulation.

[0067] Example 5

[0068] S1. Ingredients: Add 85 kg of methyl methacrylate, 15 kg of ethyl acrylate, 8 g of initiator TBPMH, and 160 g of n-octyl mercaptan to mixing tank A to prepare reaction solution A; add 1 g of tert-dodecyl mercaptan disulfide and 100 g of octadecyl alcohol to mixing tank B, maintain the temperature inside the tank at 90-110℃ and fully melt and mix to prepare auxiliary agent solution A.

[0069] S2. Polymerization reaction: Add reaction solution A to reactor A to carry out the polymerization reaction, control the polymerization temperature at 135℃ and the residence time at 2h to obtain slurry A; add the slurry to reactor B for the next polymerization reaction, control the polymerization temperature at 155℃ and the residence time at 0.5h to obtain slurry B; then add slurry B and auxiliary agent solution A to reactor C through a static mixer for the next polymerization reaction, control the reaction temperature at 190℃ and the residence time at 0.5h to obtain slurry C;

[0070] S3. Extrusion devolatilization: Add slurry C to the extrusion devolatilizer, control the devolatilization temperature at 250℃, the vacuum degree at 2.5KPa, and the residence time at 5min, and obtain the product through extrusion and granulation.

[0071] Comparative Example 1

[0072] S1. Ingredients: Add 45kg of methyl methacrylate, 55kg of methyl acrylate, 7g of initiator TBPMH, and 120g of n-octyl mercaptan to mixing tank A to prepare reaction solution A; add 1g of tert-dodecyl mercaptan disulfide and 100g of octadecanol to mixing tank B, maintain the temperature inside the tank at 90-110℃ and fully melt and mix to prepare auxiliary agent solution A.

[0073] S2. Polymerization reaction: Add reaction solution A to reactor A to carry out the polymerization reaction, control the polymerization temperature at 135℃ and the residence time at 2h to obtain slurry A; add the slurry to reactor B for the next polymerization reaction, control the polymerization temperature at 155℃ and the residence time at 0.5h to obtain slurry B; then add slurry B and auxiliary agent solution A to reactor C through a static mixer for the next polymerization reaction, control the reaction temperature at 190℃ and the residence time at 0.5h to obtain slurry C;

[0074] S3. Extrusion devolatilization: Add slurry C to the extrusion devolatilizer, control the devolatilization temperature at 250℃, the vacuum degree at 2.5KPa, and the residence time at 5min, and obtain the product through extrusion and granulation.

[0075] Comparative Example 2

[0076] S1. Ingredients: Add 75kg of methyl methacrylate, 25kg of methyl acrylate, 8g of initiator TBPMH, and 150g of n-octyl mercaptan to mixing tank A to prepare reaction solution A; add 20g of tert-dodecyl mercaptan disulfide and 100g of octadecyl alcohol to mixing tank B, maintain the temperature inside the tank at 90-110℃ and fully melt and mix to prepare auxiliary agent solution A;

[0077] S2. Polymerization reaction: Add reaction solution A to reactor A to carry out the polymerization reaction, control the polymerization temperature at 135℃ and the residence time at 2h to obtain slurry A; add the slurry to reactor B for the next polymerization reaction, control the polymerization temperature at 155℃ and the residence time at 0.5h to obtain slurry B; then add slurry B and auxiliary agent solution A to reactor C through a static mixer for the next polymerization reaction, control the reaction temperature at 190℃ and the residence time at 0.5h to obtain slurry C;

[0078] S3. Extrusion devolatilization: Add slurry C to the extrusion devolatilizer, control the devolatilization temperature at 250℃, the vacuum degree at 2.5KPa, and the residence time at 5min, and obtain the product through extrusion and granulation.

[0079] Comparative Example 3

[0080] S1. Ingredients: Add 75kg of methyl methacrylate, 25kg of methyl acrylate, 8g of initiator TBPMH, and 150g of n-octyl mercaptan to mixing tank A to prepare reaction solution A; add 100g of octadecyl alcohol to mixing tank B, maintain the temperature inside the tank at 90-110℃ and fully melt and mix to prepare auxiliary agent solution A.

[0081] S2. Polymerization reaction: Add reaction solution A to reactor A to carry out the polymerization reaction, control the polymerization temperature at 135℃ and the residence time at 2h to obtain slurry A; add the slurry to reactor B for the next polymerization reaction, control the polymerization temperature at 155℃ and the residence time at 0.5h to obtain slurry B; then add slurry B and auxiliary agent solution A to reactor C through a static mixer for the next polymerization reaction, control the reaction temperature at 190℃ and the residence time at 0.5h to obtain slurry C;

[0082] S3. Extrusion devolatilization: Add slurry C to the extrusion devolatilizer, control the devolatilization temperature at 250℃, the vacuum degree at 2.5KPa, and the residence time at 5min, and obtain the product through extrusion and granulation.

[0083] The copolymers prepared in each embodiment and comparative example were subjected to tests for molecular weight, melt index, glass transition temperature, YI value, heat resistance, and residual monomers. The test results are shown in Tables 2 and 3.

[0084] Table 2 Results of performance tests before heat resistance

[0085]

[0086] Table 3 Results of heat resistance performance tests

[0087]

[0088]

[0089] The test results of the thermoplastic acrylate copolymers with excellent properties prepared by Examples 1-5 show that, within the scope of the claims, it is possible to prepare thermoplastic acrylate copolymers with high heat resistance and low residue, and with better heat decomposition resistance.

[0090] Comparing Comparative Example 1 with Example 3, the amount of methyl acrylate monomer added in Comparative Example 1 was increased from 25 kg to 55 kg, and the product Tg decreased to 56.3 °C, exceeding the lower limit. At the same time, in order to maintain the melt index of 270 °C and 2.16 kg within the range of 50-60 g / 10 min, the amount of n-octyl mercaptan was reduced from 150 g to 120 g, which significantly reduced its heat resistance. After heating, the proportion of molecular weight segments <10,000 increased to 1.89%, which would cause defects in the film manufacturing process.

[0091] Comparing Comparative Example 2 with Example 3, the amount of tert-dodecyl disulfide added in Comparative Example 2 was increased from 1g to 20g, but its 3mm YI value after heat resistance increased by 0.21, and the yellowing was too obvious, which would cause the manufactured film to have a base color defect.

[0092] By comparing Comparative Example 3 with Examples 1-3, it was found that no molecular chain stabilizer was added in Comparative Example 3. Before heat resistance, the proportion of molecular weight segments <10,000 was 2.8%, and after heat resistance, the proportion of molecular weight segments <10,000 reached 3.5%, with a residual amount as high as 5,500 ppm, which would cause serious processing defects.

Claims

1. A thermoplastic acrylate polymer resistant to heat degradation, prepared from the following raw materials: I. First comonomer: methacrylate monomer, 50-100 parts by weight, preferably 60-90 parts by weight; II. Second comonomer: acrylate monomer, 1-50 parts by weight, preferably 10-40 parts by weight; The glass transition temperature of the polymer is controlled at 60-90℃, and 0.00001-0.00015 parts by mass of molecular chain stabilizer are added to the polymer. The molecular weight distribution of the polymer is 1.7-1.9, and the proportion of small molecule polymers with a weight average molecular weight of less than 10,000 is controlled at 0.5-1.5 mol%. This is based on the polymer being 100%.

2. The polymer according to claim 1, characterized in that, The polymer has a weight-average molecular weight of 50,000-200,000, preferably 100,000-150,000.

3. The polymer according to claim 1, characterized in that, The thermoplastic acrylate polymer that is resistant to heat degradation contains 1-50 wt% acrylate monomers, preferably 10-40 wt%, based on 100 wt% of all types of monomers participating in the main chain polymerization.

4. The polymer according to claim 1, characterized in that, The methacrylate monomers are selected from one or more of methyl methacrylate, ethyl methacrylate, and butyl methacrylate, preferably methyl methacrylate; the acrylate monomers are selected from one or more of methyl acrylate, ethyl acrylate, and butyl acrylate, preferably methyl acrylate and / or ethyl acrylate, more preferably methyl acrylate.

5. The polymer according to claim 1, characterized in that, The molecular chain stabilizer is selected from one or more of the following: dilauryl thiodipropionate, distearate thiodipropionate, di(tridecyl) thiodipropionate, dioctyl thiosuccinate, benzyl thiobenzoate, dimethyl dithiocarbonate, and tert-dodecyl disulfide.

6. A method for preparing the polymer according to any one of claims 1-5, comprising the following steps: S1: Ingredients: Reaction solution A is prepared by mixing methacrylate monomers, acrylate monomers, initiators, and chain transfer agents; The molecular chain stabilizer and the mold release agent are heated and melted to prepare auxiliary agent liquid A; S2: Polymerization reaction: Reaction solution A is subjected to polymerization reaction to prepare slurry A; slurry A is subjected to polymerization reaction to prepare slurry B; slurry B is mixed with auxiliary agent solution A to obtain slurry C; S3: Extrusion devolatilization: Slurry C is added to a devolatilizer, undergoes multi-stage devolatilization, and is then extruded through a die to obtain the product.

7. The method according to claim 6, characterized in that, The initiator in S1 is one or more of the following: benzoyl peroxide, tert-butyl peroxide-2-ethylhexanoate, tert-butyl peroxide-isobutyrate, tert-butyl peracetic acid, dicumyl peroxide, 1,1-bis-(tert-butylperoxide)-3,3,5-trimethylcyclohexane, tert-butyl peroxide-3,5,5-trimethylhexanoate, tert-butyl peroxide-benzoate, tert-butyl cumene peroxide, cumene hydroperoxide, and tert-butyl hydroperoxide; preferably tert-butyl peroxide-3,5,5-trimethylhexanoate and / or dicumyl peroxide, more preferably tert-butyl peroxide-3,5,5-trimethylhexanoate; and / or... The amount of initiator added in reaction solution A of S1 is 0.001-0.015 parts by mass per 100 parts by mass of monomer, preferably 0.005-0.009 parts by mass, wherein the monomer comprises methacrylate monomers and acrylate monomers.

8. The method according to claim 6, characterized in that, The chain transfer agent S1 is one or more selected from n-butanethiol, tert-butanethiol, n-octanethiol, isooctanethiol, n-dodecylthiol, and tert-dodecylthiol, preferably n-octanethiol; and / or, The chain transfer agent is added at a ratio of 0.05-0.3 parts by weight per 100 parts by weight of monomer, preferably 0.1-0.25 parts by weight, wherein the monomer comprises methacrylate monomers and acrylate monomers.

9. The method according to claim 6, characterized in that, The molecular chain stabilizer addition ratio is 0.0005-0.01 parts by mass per 100 parts by mass of slurry A, preferably 0.001-0.005 parts by mass.

10. The method according to claim 6, characterized in that, The release agent is one or more of alkyl alcohols or alkyl acids with 1-30 carbon atoms, preferably one or more of alkyl alcohols or alkyl acids with 6-20 carbon atoms, more preferably one or more of alkyl alcohols or alkyl acids with 14-18 carbon atoms; further preferably one or more of hexadecyl alcohol, octadecyl alcohol, hexadecanoic acid, and octadecanoic acid, more preferably octadecyl alcohol, and the addition ratio is 0.05-0.3 parts by weight per 100 parts by weight of slurry A, preferably 0.08-0.12 parts by weight.

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