Reactive compatilizer and application thereof in TPU / POM (thermoplastic polyurethane / polyoxymethylene) blending modification

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a reactive compatilizer and application of the reactive compatilizer in TPU / POM blending modification, and the reactive compatilizer comprises the following components in parts by weight: a polyformaldehyde-b-polyoxazoline block copolymer; maleic anhydride; and dicumyl peroxide; an antioxidant 1010; the polyoxazoline block accounts for 28 to 32 weight percent, and the number-average molecular weight of the polyoxazoline block is 3000 to 5000 g / mol. A main chain is of a block structure or a grafted structure, strong physical adsorption is formed by the block structure or the grafted structure and POM, and part of chain segments can be embedded into the edge of a crystalline region of POM due to the similar structure; chemical / physical double bonding is formed with TPU, the thickness of an interface layer is increased, the bonding strength is high, and stress can be efficiently transmitted. According to the invention, the size of the TPU dispersed phase is reduced from the micron level to the nano level, and the loss of tensile strength and rigidity is reduced while the toughness is improved. The early fracture caused by stress concentration is avoided, and meanwhile, the interference on the crystal structure of the POM matrix is small.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a reactive compatibilizer and its application in TPU / POM blend modification. Background Technology

[0002] Polyoxymethylene (POM) is a type of highly crystalline, high-melting-point thermoplastic engineering plastic, typically classified into homopolymers and copolymers. Homopolymer POM has a melting point of 175-183℃, a crystallinity of 75-85%, a tensile strength of 70 MPa, an elongation at break of 40%, and a molding shrinkage of 2.0-2.5%. Copolymer POM has a melting point of 160-165℃, a crystallinity of 70-75%, a tensile strength of 62 MPa, an elongation at break of 60%, and a molding shrinkage of 2.5-3.0%. It possesses excellent physical and mechanical properties, exhibiting high specific strength and stiffness, excellent corrosion resistance, wear resistance, self-lubrication, and creep resistance. POM's specific strength and specific stiffness are very close to those of metals, and over 80% of its products are used to replace non-ferrous metals and alloys such as copper, zinc, and aluminum in the automotive industry, machinery manufacturing, precision instruments, electronics, agriculture, and daily consumer goods. Among the five major engineering plastics, POM's demand ranks second only to polyamide and polycarbonate.

[0003] Although POM possesses excellent overall properties, it also suffers from drawbacks such as low impact toughness, high notch sensitivity, poor thermal stability, and a high coefficient of friction, which significantly limit its application in various fields. In particular, due to its high crystallinity, POM easily generates large spherulites during molding and processing. These large spherulites tend to form stress concentration points when the material is subjected to impact, leading to material failure. This results in high notch sensitivity and low notched impact strength for POM, limiting its performance to low-load, low-speed operation. Therefore, toughening POM is of great importance.

[0004] Due to its insufficient toughness, POM is prone to breakage during parts processing, thus requiring toughening modification. Currently, the most common method for toughening POM is modification with thermoplastic elastomers. Commonly used thermoplastic polyurethanes (TPU), thermoplastic polyester elastomers (TPEE), ethylene propylene diene monomer (EPDM), styrene-butadiene rubber (SBR), acrylate elastomers (ACE), and polyolefin elastomers (POE) are among the most studied POM toughening systems, especially TPU / POM and POM / ACE.

[0005] Currently, TPU is widely recognized as the most effective toughening agent for POM elastomers. Due to the hydrogen bonds formed between TPU and POM, it exhibits better compatibility compared to other materials. However, while increasing the amount of TPU added improves toughness, it may significantly reduce the stiffness, tensile strength, and dimensional stability of POM. Furthermore, the two materials have a significant difference in polarity. POM is a highly crystalline, non-polar material, while TPU is a polar elastomer; their poor compatibility can easily lead to phase separation, affecting mechanical properties. Therefore, it is necessary to select appropriate compatibilizer specifications and addition amounts.

[0006] The existing compatibilizer PE-g-MAH uses non-polar polyethylene (PE) as the main chain, grafted with a small amount of polar maleic anhydride (MAH) functional groups (typically grafted at a rate of 1-5%). Its design aims to utilize the compatibility of the PE main chain with non-polar polymers (such as PE and PP), and the hydrogen or covalent bonds formed between the carboxyl groups (-COOH) of MAH and the amino (-NH2) and hydroxyl groups (-OH) of polar polymers (such as PA and PET), to achieve a "non-polar-polar" interfacial bridging.

[0007] PE-g-MAH has certain limitations. The PE backbone (-CH2-CH2-) and the POM backbone (-O-CH2-) have significant structural differences, and there is a lack of specific interactions between molecules (such as hydrogen bonds and van der Waals forces between ether bonds), resulting in poor compatibility with POM. It relies solely on the reaction between the -COOH of MAH and the -NH- or -OH of TPU, but the reactivity is low (the reaction between carboxyl and amino groups requires high temperature and is slow). Furthermore, the interfacial bonding between the PE backbone and POM is weak, which cannot effectively reduce the interfacial tension of TPU / POM and easily leads to phase separation.

[0008] The mechanism of action of PE-g-MAH mainly relies on "physical compatibility + weak chemical interaction": the PE backbone is compatible with the nonpolar phase (such as PE) through molecular chain entanglement, and the -COOH of MAH forms hydrogen bonds or salt bonds (weak interactions) with the -NH2 of the polar phase (such as PA). For TPU / POM, due to the lack of affinity with POM, it can only form a weak bond on the TPU side, resulting in a thin interfacial layer with low strength. The effect of PE-g-MAH in TPU / POM is only to slightly improve phase separation (due to limited improvement in compatibility), the toughening effect is not significant, and it cannot suppress the decrease in tensile strength and stiffness (weak interfacial bonding, stress concentration still exists). Summary of the Invention

[0009] The purpose of this invention is to solve the problems of poor compatibility, weak interfacial bonding, and difficulty in balancing toughening and strength caused by differences in polarity and crystal structure in the prior art of TPU / POM blend modification.

[0010] To achieve the above objectives, the present invention provides a reactive compatibilizer comprising the following components by weight: 100 parts of polyoxymethylene-b-polyoxazoline block copolymer; Maleic anhydride 1.5-2.2 parts; 0.15-0.25 parts of dicumyl peroxide; Antioxidant 1010: 0.2-0.4 parts; The polyoxymethylene-b-polyoxazoline block copolymer contains 28-32 wt% polyoxazoline blocks and has a number average molecular weight of 3000-5000 g / mol.

[0011] Preferably, the molecular weight distribution (PDI) of the polyoxymethylene-b-polyoxazoline block copolymer is 1.2-1.5.

[0012] Preferably, the polyoxymethylene-b-polyoxazoline block copolymer contains trioxymethylene, and the polyoxazoline block is a homopolymer of 2-phenyl-2-oxazoline, or a copolymer of 2-phenyl-2-oxazoline and 2-methyl-2-oxazoline in a molar ratio of 1:0.8-1.2.

[0013] Preferably, the compatibilizer has a grafting rate of 1.8-2.0%, a melt index of 3-5 g / 10 min at 190℃ / 2.16 kg, an oxazoline ring retention rate of ≥85%, and a hydrogen bonding energy with TPU of ≥15 kJ / mol.

[0014] This invention also provides a method for preparing a reactive compatibilizer, the specific steps of which are as follows: S1. Under nitrogen protection, trioxymethylene is dissolved in an organic solvent, a chain transfer agent is added, the temperature is lowered to -15 to -10℃, a catalyst is added, and the polymerization is catalyzed for 30 minutes to form active POM chains. S2. Add oxazoline monomer or its mixed monomers, react at -10--5℃ for 4-5 hours, terminate the reaction, precipitate and dry to obtain block copolymer; S3. The block copolymer, maleic anhydride, dicumyl peroxide, and antioxidant 1010 are melt-grafted, and the extrusion temperature is controlled in stages: 180±2℃ for the feeding stage, 190±2℃ for the compression stage, and 200±2℃ for the metering stage.

[0015] Preferably, the chain transfer agent in S1 is methyl acetal, the catalyst is boron trifluoride diethyl ether complex, and the melt grafting in S3 is carried out in a twin-screw extruder with a screw speed of 200-300 rpm and a vacuum devouring pressure ≤-0.08 MPa.

[0016] This invention also provides the application of a reactive compatibilizer in the TPU / POM blend modification.

[0017] Preferably, the amount of compatibilizer added in the blending modification is 1-5 wt% of the total weight of TPU / POM.

[0018] Preferably, the dispersed phase size of TPU in the blend modification is 1-3 μm.

[0019] Compared with the prior art, the advantages of this invention are: 1. This invention achieves bidirectional affinity through molecular structure design, containing segments affinity for POM and functional groups affinity for TPU. The main chain is a block or graft structure, rather than a simple polyolefin main chain. It forms strong physical adsorption with POM through segmental structure matching; some segments can even embed into the edges of POM's crystalline regions due to structural similarity. With TPU, it forms a dual chemical / physical bond through functional group reactions or hydrogen bonding, increasing the interfacial layer thickness and increasing the bonding strength, thus efficiently transferring stress. It exhibits good compatibility with the non-polar POM matrix and forms strong interactions with the polar TPU elastomer. Furthermore, by controlling the ratio of molecular chain rigidity to flexibility, it reduces the negative impact on the strength and rigidity of the blend.

[0020] 2. This invention strengthens interfacial bonding, reducing the TPU dispersed phase size from the micrometer level to the nanometer level, thereby improving toughness while minimizing the loss of tensile strength and rigidity. It avoids premature fracture caused by stress concentration, and the crystal structure of the POM matrix is ​​less disturbed. Detailed Implementation

[0021] The terms used in this invention, unless otherwise stated, generally have the meanings commonly understood by those skilled in the art.

[0022] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art.

[0023] The reagents used in the following examples were obtained through common commercial channels. Experimental procedures and conditions not specified are in accordance with conventional procedures and conditions in the art.

[0024] The specific implementation of the present invention will be described below with reference to the embodiments.

[0025] This invention provides a reactive compatibilizer, the components of which include 100 parts of polyoxymethylene-b-polyoxazoline block copolymer; 2.2 parts of maleic anhydride; 0.25 parts of dicumyl peroxide; and 0.4 parts of antioxidant 1010. The specific preparation method is as follows: S1. Under nitrogen protection, trioxymethylene is dissolved in an organic solvent, a chain transfer agent is added, the temperature is lowered to -10℃, a catalyst is added, and the polymerization is catalyzed for 30 minutes to form active POM chains. S2. Add oxazoline monomer or a mixture of monomers, react at -5℃ for 5 hours, terminate the reaction, precipitate and dry to obtain block copolymer; S3. The block copolymer, maleic anhydride, dicumyl peroxide, and antioxidant 1010 are melt-grafted, and the extrusion temperature is controlled in stages: 182℃ for the feeding stage, 192℃ for the compression stage, and 202℃ for the metering stage.

[0026] The reactive compatibilizer was finally obtained.

[0027] The reactive compatibilizer provided by this invention is applied to the TPU / POM blend modification.

[0028] The preparation steps for TPU / POM blend modification are existing technologies, and the required raw materials include POM; TPU; antioxidant 1010; ultraviolet absorber; light stabilizer; lubricant; compatibilizer; silane coupling agent; and acid scavenger.

[0029] Commonly used POM specifications include: POM 100P from DuPont (USA), POM M25-44, POM M90-44 from Polyplastics (Japan), and M90 from Yunnan Yuntianhua, etc. The POM used in Example 1 and Comparative Example 1 provided in this invention is POM 100P from DuPont (USA).

[0030] Thermoplastic polyurethane elastomers (TPUs) include polycaprolactone-based TPUs, polybutylene adipate-based TPUs, and polytetrahydrofuran ether-based TPUs, among which polycaprolactone copolyester-based TPUs exhibit the best overall toughening mechanical properties. When this type of TPU is melt-blended with POM, the viscosity is matched, the dispersion is uniform, and the toughening effect is superior to other TPUs. The modification effect of polyester-type TPUs is significantly better than that of polyether-type TPUs. The "soft segments" of polyester-type polyurethanes contain ester groups, while the "soft segments" of polyether-type polyurethanes contain ether bonds. Ester groups are more likely to attract hydrogen atoms on the POM molecular chain than ether bonds, thereby enhancing the interfacial interaction forces. The TPU hardness is 80-90A, preferably 85A. Lianjing 185AL is used; the TPUs in Example 1 and Comparative Example 1 provided in this invention are both Lianjing 185AL.

[0031] Antioxidant 1010 can be selected from 2,6-di-tert-butyl-p-cresol, pentaerythritol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1010), and bis(3,5-di-tert-butylphenyl)pentaerythritol diphosphite (Irganox 1010). 126), UV absorbers N-(ethoxycarbonylphenyl)-N'-methyl-N'-phenylamidine (UV-1), N,N'-bis(4-ethoxyformylphenyl)-N-benzylformamidine (UV-3), 2-(2H-benzotriazol-2-yl-)4-(1,1,3,3-tetramethylbutyl)phenol (Tinuvin 329), hindered amine light stabilizer succinic acid and (polymer of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) (Tinuvin 622), the antioxidants in Example 1 and Comparative Example 1 provided by the present invention are all selected from pentaerythritol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1010).

[0032] The UV absorber is UV-3, and the light stabilizer is Tinuvin 622.

[0033] The lubricant can be selected from montan wax, erucamide, oleamide, ethylene bis-stearamide wax (EBS), etc., and one or more combinations thereof can be selected. The lubricant used in Example 1 and Comparative Example 1 provided by the present invention is ethylene bis-stearamide wax (EBS).

[0034] In Example 1 of this invention, the compatibilizer selected is the reactive compatibilizer (POM-b-POX-g-MAH) provided by this invention, and in Comparative Example 1, the compatibilizer selected is SEBS-g-MAH.

[0035] The silane coupling agent can be selected from one of γ-methacryloxypropyltrimethoxysilane (KH-570), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), and γ-aminopropyltriethoxysilane (KH-550). The silane coupling agent in Example 1 and Comparative Example 1 provided by the present invention is γ-methacryloxypropyltrimethoxysilane (KH-570).

[0036] The acid absorbent can be magnesium hydroxide, aluminum hydroxide, or aluminum magnesium hydrotalcite DHT-4A. In both Example 1 and Comparative Example 1 provided by this invention, the acid absorbent is magnesium hydroxide. Example

[0037] The reactive compatibilizer prepared by the above method was applied to the TPU / POM blend modification to obtain the TPU / POM blend material of Example 1.

[0038] The TPU / POM blend material in Example 1 comprises the following components by weight percentage: POM 63%; TPU (185AL) 30%; antioxidant 1010 0.5%; UV absorber UV-3 0.3%; light stabilizer Tinuvin 622 0.3%; lubricant EBS 0.1%; compatibilizer (POM-b-POX-g-MAH) prepared according to the present invention 5%; silane coupling agent 0.7%; and acid scavenger 0.1%.

[0039] Comparative Example 1 The components of the blend material in Comparative Example 1, by weight percentage, are as follows: POM 63%; TPU (185AL) 30%; antioxidant 1010 0.5%; UV absorber UV-3 0.3%; light stabilizer Tinuvin 622 0.3%; lubricant EBS 0.1%; compatibilizer (SEBS-g-MAH) 5%; silane coupling agent 0.7%; and acid scavenger 0.1%.

[0040] The preparation methods of the blends in Example 1 and Comparative Example 1 are existing technologies.

[0041] The properties of the TPU / POM modified materials of Example 1 and Comparative Example 1 were compared, and the comparison results are shown in Table 1 below: Table 1 Performance / Components Comparative Example 1 (SEBS-g-MAH compatibilizer selected) Example 1 (Compatibilizer selected in this invention for the preparation of POM-b-POX-g-MAH) Tensile strength (MPa) 45±2 58±3 Elongation at break (%) 150±10 210±15 Flexural modulus (MPa) 1500±50 1950±80 Notched impact strength (kJ / m²) 22±1 34±2 As shown in Table 1, when the reactive compatibilizer provided by this invention is applied to the preparation of TPU / POM blends, the resulting TPU / POM blends exhibit improved tensile strength, elongation at break, flexural modulus, and notched impact strength.

[0042] The above is a detailed description of the embodiments, which is intended to enable those skilled in the art to correctly understand and use the present invention. Any improvements or modifications to technical solutions obtained by those skilled in the art based on the present invention and on the existing technology, without innovative effort but only through analysis, analogy, or limited enumeration, should be within the scope of protection defined by the claims.

Claims

1. A reactive compatibilizer, characterized in that, The components are included by weight as follows: 100 parts of polyoxymethylene-b-polyoxazoline block copolymer; Maleic anhydride 1.5-2.2 parts; 0.15-0.25 parts of dicumyl peroxide; Antioxidant 1010: 0.2-0.4 parts; The polyoxymethylene-b-polyoxazoline block copolymer contains 28-32 wt% polyoxazoline blocks and has a number average molecular weight of 3000-5000 g / mol.

2. The reactive compatibilizer as described in claim 1, characterized in that, The molecular weight distribution (PDI) of the polyoxymethylene-b-polyoxazoline block copolymer is 1.2-1.

5.

3. The reactive compatibilizer as described in claim 1, characterized in that, The polyoxymethylene-b-polyoxazoline block copolymer contains trioxymethylene, and the polyoxazoline block is a homopolymer of 2-phenyl-2-oxazoline, or a copolymer of 2-phenyl-2-oxazoline and 2-methyl-2-oxazoline in a molar ratio of 1:0.8-1.

2.

4. The reactive compatibilizer as described in claim 1, characterized in that, The compatibilizer has a grafting rate of 1.8-2.0%, a melt index of 3-5 g / 10 min at 190℃ / 2.16 kg, an oxazoline ring retention rate of ≥85%, and a hydrogen bonding energy with TPU of ≥15 kJ / mol.

5. A method for preparing a reactive compatibilizer as described in any one of claims 1-4, characterized in that, The specific steps are as follows: S1. Under nitrogen protection, trioxymethylene is dissolved in an organic solvent, a chain transfer agent is added, the temperature is lowered to -15 to -10℃, a catalyst is added, and the polymerization is catalyzed for 30 minutes to form active POM chains. S2. Add oxazoline monomer or its mixed monomers, react at -10--5℃ for 4-5 hours, terminate the reaction, precipitate and dry to obtain block copolymer; S3. The block copolymer, maleic anhydride, dicumyl peroxide, and antioxidant 1010 are melt-grafted, and the extrusion temperature is controlled in stages: 180±2℃ for the feeding stage, 190±2℃ for the compression stage, and 200±2℃ for the metering stage.

6. The method for preparing the reactive compatibilizer as described in claim 5, characterized in that, The chain transfer agent in S1 is methyl acetal, and the catalyst is boron trifluoride diethyl ether complex. The melt grafting in S3 is carried out in a twin-screw extruder with a screw speed of 200-300 rpm and a vacuum devouring pressure ≤-0.08 MPa.

7. The application of a reactive compatibilizer as described in any one of claims 1-4 in the TPU / POM blend modification.

8. The application of the reactive compatibilizer as described in claim 7 in the TPU / POM blend modification, characterized in that, The amount of compatibilizer added in the blend modification is 1-5 wt% of the total weight of TPU / POM.

9. The application of the reactive compatibilizer as described in claim 7 in the TPU / POM blend modification, characterized in that, The dispersed phase size of TPU in the blend modification is 1-3 μm.