Polyformaldehyde resin composition capable of forming film as well as preparation method and application thereof

Abstract

The invention relates to the field of high polymer materials, and discloses a film-forming polyformaldehyde resin composition and a preparation method and application thereof.The film-forming polyformaldehyde resin composition is prepared from, by mass, 3-5 parts of simethicone, 3-5 parts of white oil, 0.1-1 part of calcium stearate, 0.1-1 part of phthalic ester, 85-95 parts of polyformaldehyde resin and 0.05-1 part of antioxidant. According to the invention, through overall optimization of the formula and the preparation process of the polyformaldehyde resin composition, the crystallization property and the fluidity of polyformaldehyde are adjusted, so that the polyformaldehyde is more suitable for film casting, and meanwhile, the scheme also can consider the mechanical property of the material.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and particularly to a film-forming polyoxymethylene resin composition, a preparation method thereof, and an application thereof. Background Art

[0002] As a kind of semi-crystalline polymer with high density and high crystallinity, polyoxymethylene (POM) has a regular chemical structure and a closely ordered molecular chain arrangement. This unique molecular structure endows polyoxymethylene with extremely excellent wear resistance. In a dynamic friction environment, it can significantly reduce the wear rate and extend the service life; its fatigue resistance is also very prominent and can withstand long-term and high-frequency stress cycles without failure. At the same time, polyoxymethylene has excellent electrical insulation properties and can maintain stable insulation characteristics within a wide range of temperatures and frequencies, and has good solvent resistance, showing high chemical stability to common organic solvents. The polyoxymethylene film material prepared based on the polyoxymethylene resin fully inherits the excellent properties of the polyoxymethylene resin, especially its outstanding performance in electrical insulation, which makes it have broad application prospects in fields such as electronic devices with strict insulation requirements. It is often used as a conveyor belt for rotating parts to meet the transmission requirements of high precision and high stability.

[0003] However, the high crystallinity nature of polyoxymethylene also brings great challenges to its molding and processing. Its crystallinity can usually be as high as 75%, and the crystallization kinetics process is rapid. During the molding process, once the temperature drops, the molecular chains will quickly arrange regularly, resulting in serious shrinkage. When using traditional molding processes such as traction and stretching, due to the uneven crystallization and anisotropic shrinkage of polyoxymethylene, it is extremely easy to cause uneven stress distribution during the stretching process, which in turn leads to uneven stretching of the film material, causing wrinkles on the surface of the film material, and even cracking in severe cases, greatly increasing the operation difficulty of the stretching process. Moreover, when applying general film-forming methods to ordinary polyoxymethylene, due to the special crystallization behavior and rheological properties of polyoxymethylene, it is very difficult to prepare a polyoxymethylene film product with a smooth surface, uniform thickness, and stable performance, which greatly limits the wide application of polyoxymethylene film materials in high-end fields.

[0004] Based on the above problems, in the prior art, ordinary polyoxymethylene is usually modified to adjust the crystallization performance and fluidity of polyoxymethylene and improve the stretching performance, so as to obtain a polyoxymethylene film product with uniform thickness and relatively high tensile strength. The current modification methods usually include:

[0005] 1. Filling and reinforcing modification: Adding glass fiber, carbon fiber, mineral or other fillers to enhance the mechanical properties of POM. This method can significantly improve the stiffness, hardness and tensile strength of the material. However, it may reduce the toughness and processing fluidity of the material; inappropriate filler selection or poor dispersion will lead to a decrease in the surface quality and uniformity of the material.

[0006] 2. Blending modification: Blend POM with other polymers (such as ABS, PC, etc.) to improve its specific properties. This method can adjust the comprehensive properties of the material according to requirements, such as increasing flexibility or improving weather resistance. However, the compatibility between polymers may be poor, affecting the stability and performance consistency of the final product; the blending process is complex and requires precise control of ratios and technical parameters.

[0007] 3. Toughening modification: Add elastomers or thermoplastic elastomers (such as SEBS, POE, etc.) to improve the impact strength of POM. This method can effectively improve the elongation at break and impact resistance of the material. However, the addition of toughening agents usually sacrifices some rigidity and hardness; if the toughening agent is not evenly dispersed, local performance differences may occur.

[0008] 4. Chemical modification: Change the molecular chain structure of POM by grafting, crosslinking, etc. to improve its properties. This method can directly optimize specific properties, such as improving heat resistance or weather resistance. However, the chemical modification process is complex and costly; sometimes new unstable factors may be introduced, affecting the overall performance of the material.

[0009] Therefore, there is an urgent need to develop a new film-forming polyoxymethylene resin composition and its preparation method, aiming to balance the casting film-forming property and mechanical properties of the material. Summary of the Invention

[0010] The present invention aims to provide a film-forming polyoxymethylene resin composition, its preparation method and application, to solve the problem that the modified polyoxymethylene in the prior art is difficult to balance the mechanical properties and casting film-forming property of the material.

[0011] To achieve the above object, the present invention adopts the following technical solution: A film-forming polyoxymethylene resin composition, in parts by mass, the raw materials include 3 - 5 parts of dimethyl silicone oil, 3 - 5 parts of white oil, 0.1 - 1 part of calcium stearate, 0.1 - 1 part of phthalate ester, 85 - 95 parts of polyoxymethylene resin, and 0.05 - 1 part of antioxidant.

[0012] Preferably, as an improvement, the melt index of the polyoxymethylene resin is 3 - 70 g / 10 min (190 °C / 2.16 kg), the density is 1.39 - 1.41 g / cm 3 , and the melting point is 165 °C - 170 °C.

[0013] Preferably, as an improvement, the antioxidant is at least one of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], diethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], and tris(2,4-di-tert-butylphenyl) phosphite.

[0014] Preferably, as an improvement, the white oil is 5# white oil with a viscosity of 4.726 mm 2 / s, density 0.823g / cm 3 , flash point 124℃.

[0015] Preferably, as an improvement, the viscosity of dimethyl silicone oil is 500-50000 cst; calcium stearate meets the qualified product requirements of standard HGT2424-1993; and titanate is a phthalate substance, including at least one of di(2-ethylhexyl) phthalate and dibutyl phthalate.

[0016] Preferably, as an improvement, the viscosity of dimethyl silicone oil is 5000 cst; the calcium content of calcium stearate is 6.5±0.5%, the free acid is ≤0.5%, and the fineness is ≥99.5% passing through a 0.075 mm sieve; and the titanate is dibutyl phthalate.

[0017] Preferably, as an improvement, a method for preparing a film-forming polyoxymethylene resin composition comprises the following steps:

[0018] Step 1: fully mix the polyoxymethylene resin and white oil to obtain system I;

[0019] Step 2: Add phthalate, dimethyl silicone oil and antioxidant into system I and stir evenly;

[0020] Step 3: melt-extrude, cool and granulate the mixed material through a twin-screw extruder to obtain film-forming polyoxymethylene.

[0021] Preferably, as an improvement, in step 2, titanate is first added to make phthalate evenly dispersed on the surface of polyoxymethylene resin particles; and then dimethyl silicone oil and antioxidant are added and stirred evenly.

[0022] Preferably, as an improvement, in step three, the screw speed in the extrusion stage is 150 r / min to 200 r / min, the feed rate is 100 kg / h to 200 kg / h, and the relative vacuum degree is 0 MPa to 0.8 MPa.

[0023] Preferably, as an improvement, in step three, the temperature of each section of the extruder is 140-160°C for the feed port 1, 160-180°C for the second section, 160-190°C for the third section, 160-190°C for the fourth section, 160-180°C for the fifth section, 160-180°C for the sixth section, 160-170°C for the seventh section, 160-170°C for the eighth section, and 160-200°C for the ninth section.

[0024] The principle and advantages of this solution are as follows: In practical applications, aiming at the problem of performance defects existing in the use of pure polyoxymethylene, in the prior art, it is usually considered to modify polyoxymethylene. Aiming at the defects existing in the modified polyoxymethylene in the prior art, this technical solution comprehensively optimizes the raw material formula and preparation process of the polyoxymethylene resin composition, aiming to take into account both the tensile properties and fluidity of the material.

[0025] In terms of the formulation composition, on the basis of polyoxymethylene resin, this technical solution innovatively adds components such as dimethyl silicone oil, white oil, calcium stearate, phthalate ester, and antioxidant. The synergistic effect of these components enables the modified polyoxymethylene to have better processing performance and film-forming performance. Polyoxymethylene resin: As the basic raw material, polyoxymethylene resin itself has excellent wear resistance, fatigue resistance, electrical insulation, and solvent resistance, providing a good performance basis for the modified polyoxymethylene film. Dimethyl silicone oil: As a lubricant, dimethyl silicone oil can improve the processing performance of polyoxymethylene, reduce friction and wear, and improve the smoothness and gloss of the film. White oil: As a plasticizer, white oil can increase the flexibility and ductility of polyoxymethylene, helping to improve the tensile properties and thickness uniformity of the film. Calcium stearate and phthalate ester: As stabilizers and lubricants, calcium stearate and phthalate ester can further improve the processing stability and film-forming performance of polyoxymethylene. Antioxidant: The addition of antioxidant can delay the aging process of polyoxymethylene, improve the service life and stability of the film; and titanate and dimethyl silicone oil can synergistically achieve the purpose of regulating the flow performance of polyoxymethylene, improving its film-forming property during casting and the uniformity of the formed film.

[0026] In terms of the preparation process, the melt extrusion process is adopted, combined with specific additives (such as dimethyl silicone oil, white oil, etc.), which significantly improves the film-forming performance of polyoxymethylene. Through the precise control of the twin-screw extruder, the uniform mixing and melt extrusion of each component are realized, ensuring the quality and performance stability of the film-forming polyoxymethylene.

[0027] In summary, this technical solution adjusts the crystallization performance and fluidity of polyoxymethylene to make it more suitable for casting film while taking into account the mechanical properties of the material. The specific implementation methods include:

[0028] 1. Reduce the crystallization rate: By adding components such as dimethyl silicone oil and white oil, the crystallization rate of polyoxymethylene is reduced, so that it has enough time to flow and be evenly distributed during the molding process, thus avoiding problems such as uneven stretching, film wrinkles, and rupture.

[0029] 2. Improve the processing performance: The addition of components such as calcium stearate and phthalate ester can improve the processing performance of polyoxymethylene, making it easier to process into a film and maintaining stable performance during the processing.

[0030] 3. Improve film-forming performance: Through the melt extrusion process and a specific combination of additives, the modified polyoxymethylene has better film-forming performance, and can produce polyoxymethylene film products with uniform thickness and relatively high tensile strength. Detailed implementation manners

[0031] The following further elaborates in detail through specific implementation manners, but the implementation manners of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following implementation manners are conventional means well-known to those skilled in the art; the experimental methods used are all conventional methods; the materials, reagents, etc. used can all be obtained through commercial channels.

[0032] General description of the solution:

[0033] A film-forming polyoxymethylene resin composition, by mass, the raw materials include 3 - 5 parts of dimethyl silicone oil, 3 - 5 parts of white oil, 0.1 - 1 part of calcium stearate, 0.1 - 1 part of phthalate, 85 - 95 parts of polyoxymethylene resin, and 0.05 - 1 part of antioxidant.

[0034] Among them, the viscosity of the dimethyl silicone oil is 500 - 50000 cst, and the optimal viscosity is 5000 cst.

[0035] The white oil is 5# white oil, with a viscosity of 4.726 mm 2 / s and a density of 0.823 g / cm 3 , and a flash point of 124 °C.

[0036] The calcium content of the calcium stearate is 6.5 ± 0.5%, the free acid ≤ 0.5%, and the fineness requirement is that the passing rate through a 0.075 mm sieve ≥ 99.5%.

[0037] The titanate is a phthalate substance, including at least one of bis(2-ethylhexyl) phthalate and dibutyl phthalate, and dibutyl phthalate (DBP) is the most optimal.

[0038] The melt index of the polyoxymethylene resin is 3 - 70 g / 10 min (190 °C / 2.16 kg), the density is 1.39 - 1.41 g / cm 3 , and the melting point is 165 °C - 170 °C.

[0039] The antioxidant is at least one of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], diethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], and tris(2,4-di-tert-butylphenyl) phosphite.

[0040] A preparation method of a film-forming polyoxymethylene resin composition includes the following steps:

[0041] Step 1: Thoroughly mix polyoxymethylene resin and white oil to obtain System I;

[0042] Step 2: Add phthalate ester into System I to make it evenly disperse on the surface of polyoxymethylene resin particles; then add dimethyl silicone oil and antioxidant (pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]), and stir evenly;

[0043] Step 3: Melt-extrude, cool, and pelletize the mixed material through a twin-screw extruder to obtain film-forming polyoxymethylene.

[0044] The process parameters of the extruder are as follows: The temperature of each barrel from the feeding port 1 to the head is 140 - 160 °C at the first feeding port, 160 - 180 °C at the second section, 160 - 190 °C at the third section, 160 - 190 °C at the fourth section, 160 - 180 °C at the fifth section, 160 - 180 °C at the sixth section, 160 - 170 °C at the seventh section, 160 - 170 °C at the eighth section, 160 - 200 °C at the ninth section, the screw speed is 150 r / min - 200 r / min, the feeding rate is 100 kg / h - 200 kg / h, and the relative vacuum degree is 0 MPa - 0.8 MPa.

[0045] Examples 1 - 5 are the examples of the present invention. The component contents (parts) of the film-forming polyoxymethylene in each example are shown in Table 1 below:

[0046] Table 1

[0047] Project Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[Polyoxymethylene resin *1 > 90.7 92.2 92.2 93.5 93.5 Polydimethylsiloxane 4 3.5 3.5 3 3 Polyolefin oil, fatty acid ester 5 4 4 3 3 Antioxidant 0.1 0.1 0.1 0.1 0.1 Calcium stearate 0.1 0.1 0.1 0.2 0.2 Dibutyl phthalate 0.1 0.1 0.1 0.2 0.2

[0048] *1: The melt indices of the polyoxymethylene resins used in each example and comparative example are inconsistent. Specifically, the melt index of Example 1 is 3 g / 10 min, the melt index of Example 2 is 9 g / 10 min, the melt index of Example 3 is 27 g / 10 min, the melt index of Example 4 is 27 g / 10 min, and the melt index of Example 5 is 70 g / 10 min;

[0049] The melt index of Comparative Example 1 is 3 g / 10 min, the melt index of Comparative Example 2 is 9 g / 10 min, the melt index of Comparative Example 3 is 27 g / 10 min, the melt index of Comparative Example 4 is 27 g / 10 min, and the melt index of Comparative Example 5 is 70 g / 10 min.

[0050] Comparative Examples 1 - 5 are the comparative examples of the present invention. The component contents (parts) of the film-forming polyoxymethylene in each comparative example are shown in Table 2 below:

[0051] Table 2

[0052] Project Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Polyoxymethylene resin 94.8 95.8 95.8 96.7 96.7 Polyolefin oil, fatty acid ester 5 4 4 3 3 Antioxidant 0.1 0.1 0.1 0.1 0.1 Calcium stearate 0.1 0.1 0.1 0.2 0.2

[0053] Taking Example 1 as an example, the preparation method of the film-forming polyoxymethylene is described in detail, including the following steps:

[0054] Step 1: Add white oil to polyoxymethylene under slow stirring;

[0055] Step 2: Slowly add phthalate ester to the polyoxymethylene with white oil on its surface. After stirring for 2 minutes, add dimethyl silicone oil and antioxidant (pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]), and then stir for another 2 minutes;

[0056] Step 3: Melt-extrude, cool, and pelletize the mixed material through a twin-screw extruder to obtain the film-forming polyoxymethylene. The process parameters of the extruder are as follows: the temperature of each barrel from the feeding port 1 to the head is 140 - 160 °C at the feeding port 1, 160 - 180 °C in the second section, 160 - 190 °C in the third section, 160 - 190 °C in the fourth section, 160 - 180 °C in the fifth section, 160 - 180 °C in the sixth section, 160 - 170 °C in the seventh section, 160 - 170 °C in the eighth section, 160 - 200 °C in the ninth section, the screw speed is 150 r / min - 200 r / min, the feeding rate is 100 kg / h - 200 kg / h, and the relative vacuum degree is 0 MPa - 0.8 MPa.

[0057] Comparative Example 6

[0058] The difference between this comparative example and Example 1 is that in this comparative example, the added stearate is magnesium stearate.

[0059] Comparative Example 7

[0060] The difference between this comparative example and Example 1 is that in this comparative example, no stearate is added.

[0061] Experimental Example

[0062] Perform performance tests on the film-forming polyoxymethylene prepared in the above examples and comparative examples. The test methods are as follows:

[0063] (1) Tensile strength: Test standard ISO 527, test speed 50 mm / min;

[0064] (2) Surface resistivity: Refer to GB / T 1410 - 2006;

[0065] (3) Impact performance test: Refer to ISO 179 / 1eA;

[0066] (4) Film tensile strength test: Refer to GB / T 1040.3.

[0067] Each group was subjected to 3 repeated tests, and the test results are shown in Table 3: The front is the mechanical properties of the material (made into standard plastic parts), and the back is the mechanical properties after being made into a film. The results show that the added raw materials such as phthalate have no effect on the properties of plastic parts, but have an effect on the thickness and tensile strength of the film made of polyoxymethylene. In each embodiment of the present invention, calcium stearate and dibutyl phthalate are used in combination. Compared with the comparative example that only adds calcium stearate, it can ensure the uniformity of the film and has better tensile strength performance. And the corresponding comparative example has a thicker film thickness compared with the embodiment (such as: Example 1 and Comparative Example 1, Example 2 and Comparative Example 2), indicating that phthalate has a greater impact on the uniformity of polyoxymethylene film formation. Without adding phthalate, the film thickness cannot be further reduced. In addition, the type of stearate also has a certain impact on the properties of the material and the properties after film formation.

[0068] Table 3

[0069]

[0070] The above are only the embodiments of the present invention. Specific technical solutions and / or common knowledge such as characteristics well known in the art are not described in detail here. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A film-forming polyoxymethylene resin composition, characterized in that: Calculated by weight, the raw materials include 3-5 parts of dimethyl silicone oil, 3-5 parts of white oil, 0.1-1 parts of calcium stearate, 0.1-1 parts of phthalate, 85-95 parts of polyoxymethylene resin, and 0.05-1 parts of antioxidant.

2. The film-forming polyoxymethylene resin composition according to claim 1, characterized in that: The melt index of the polyoxymethylene resin is 3 - 70 g / 10 min (190 °C / 2.16 kg), and the density is 1.39 - 1.41 g / cm 3 , and the melting point is 165 °C - 170 °C.

3. The polyoxymethylene resin composition capable of forming a film according to claim 2, wherein: The antioxidant is at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] and tris[2,4-di-tert-butylphenyl] phosphite.

4. The film-forming polyoxymethylene resin composition according to claim 3, characterized in that: The white oil is 5# white oil, with a viscosity of 4.726 mm 2 / s and a density of 0.823 g / cm 3 , and a flash point of 124 °C.

5. The polyoxymethylene resin composition capable of forming a film according to claim 4, characterized in that: The viscosity of the dimethyl silicone oil is 500-50000 cst; the calcium stearate meets the qualified product requirements of standard HG T 2424-1993; the titanate is a phthalate substance, including at least one of di(2-ethylhexyl) phthalate and dibutyl phthalate.

6. The film-forming polyoxymethylene resin composition according to claim 5, wherein: The viscosity of the dimethyl silicone oil is 5000 cst; the calcium content of calcium stearate is 6.5±0.5%, the free acid is ≤0.5%, and the fineness is ≥99.5% passing through a 0.075 mm sieve; and the titanate is dibutyl phthalate.

7. The preparation method of a film-forming polyoxymethylene resin composition according to any one of claims 1 to 6, characterized in that, The steps include: Step 1: fully mix the polyoxymethylene resin and white oil to obtain system I; Step 2: Add phthalate, dimethyl silicone oil and antioxidant into system I and stir evenly; Step 3: melt-extrude, cool and granulate the mixed material through a twin-screw extruder to obtain film-forming polyoxymethylene.

8. The preparation method of a film-forming polyoxymethylene resin composition according to claim 7, characterized in that: In step 2, titanate is first added to make phthalate evenly dispersed on the surface of polyoxymethylene resin particles; then dimethyl silicone oil and antioxidant are added and stirred evenly.

9. The preparation method of a film-forming polyoxymethylene resin composition according to claim 8, characterized in that: In step three, the screw speed in the extrusion stage is 150 r / min to 200 r / min, the feed rate is 100 kg / h to 200 kg / h, and the relative vacuum degree is 0 MPa to 0.8 MPa.

10. The preparation method of a film-forming polyoxymethylene resin composition according to claim 9, characterized in that: In step three, the temperature of each section of the extruder is 140-160°C for feed port 1, 160-180°C for the second section, 160-190°C for the third section, 160-190°C for the fourth section, 160-180°C for the fifth section, 160-180°C for the sixth section, 160-170°C for the seventh section, 160-170°C for the eighth section, and 160-200°C for the ninth section.

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