Weather-proof repair type polyamide composition and preparation method thereof

Abstract

The invention relates to a weather-proof repair type polyamide composition and a preparation method thereof. Comprising the following components in parts by weight: 30-99 parts of polyamide resin; 0.5-5 parts of a weather-proof repairing agent; 0-50 parts of a reinforcing material; 0-30 parts of a halogen-free flame retardant; 0.5 to 5 parts of other auxiliary agents; wherein the weather-proof repairing agent is mineral inorganic gel coated with a silane coupling agent, and the mass of the silane coupling agent is 5%-15% of the mass of the mineral inorganic gel. The principle of hydrated gel is adopted, when microcracks appear on the surface of the material, exposed mineral inorganic gel encounters water to generate inorganic colloid with high transparency and high viscoelasticity, the microcracks are filled, spraying and washing are resisted, the microcracks are prevented from expanding, and the gel plugging and repairing effects are achieved. After being treated by an SAE J2527 automobile exterior decoration method for 1500h, the color difference and glossiness change is obviously reduced, the mechanical property is not influenced, and no stickiness, whitening or cracking is caused. The method is not influenced by color matching and formula systems and is widely applicable.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyamides, and particularly relates to a weather-resistant repair type polyamide composition and a preparation method thereof. Background Art

[0002] The research on the heat-oxidative aging and weather resistance of plastics has become a hot topic in the field of materials. As the top of the five major engineering plastics, nylon has a regular structure, making it have excellent chemical resistance, heat resistance, wear resistance and mechanical properties. However, the presence of strong polar groups in nylon also makes it prone to complex chemical reactions under outdoor conditions of light, water vapor, heat and oxygen, which in turn leads to its degradation and aging. It is known from research that carbon black shows excellent outdoor weather resistance in rubber and plastics by absorbing or scattering ultraviolet light and reducing the direct action of ultraviolet light on plastics. In the crystal structure of silica, silicon atoms are located at the center of a regular tetrahedron, and four oxygen atoms are located at the four vertices of the regular tetrahedron. This structure makes silica have good stability under light. However, for light-colored and colored nylon products with strict color requirements, it is difficult to meet the requirements for weather resistance. Currently, the more common improvement methods in industry are as follows:

[0003] (1) From the perspective of weather-resistant additives: Patent CN107446349B discloses a UV-resistant flame-retardant nylon composite material and a preparation method thereof. By selecting specific ultraviolet light absorbers, hindered amine light stabilizers and antioxidants for compounding, the UV-resistant aging characteristics of the flame-retardant nylon composite material are greatly improved. Patent CN106280480A discloses an anti-ultraviolet nano-calcium carbonate modified composite material for nylon. By mixing an ultraviolet light absorber with a nano-calcium carbonate masterbatch and then heating and melting, the ultraviolet light absorber is not easily migrated, greatly prolonging the timeliness of the anti-ultraviolet function. Patent CN1114773838A discloses the application of a 3-phenyl-2-acrylic acid structure compound in a weather-resistant polyamide material. Through the synergistic effect of the 3-phenyl-2-acrylic acid structure compound with conventional weather-resistant agents such as ultraviolet light absorbers and hindered amine light stabilizers, the weather resistance of the polyamide material can be greatly improved.

[0004] (2) Angle of toner and filler: Patent CN113861672B discloses an anti-aging halogen-free flame-retardant nylon composite material and its preparation method. Without adding ultraviolet absorbers and light stabilizers additionally, by compounding titanate mineral filler with blue-phase titanium dioxide and zinc sulfide, the increase in the yellowness value of the anti-aging halogen-free flame-retardant nylon composite material caused by simply using titanium dioxide is partially offset. Patent CN113201216B discloses a nylon with high color stability and its preparation method. By modifying the product with cerium sulfide as a colorant in a specific content, the obtained nylon has firm coloring and significantly improves its discoloration after moisture absorption. Patent CN114752214B discloses a weather-resistant nylon composite material and its preparation method. Nano-zirconia is surface-modified with polydopamine, so that a polydopamine layer is formed on the surface of nano-zirconia. Graphene is surface-modified with 1,3,6,8-tetraaminopyrene, bringing a large number of amino groups and pyrene. Pyrene has a large π-conjugated system and has excellent ultraviolet absorption performance.

[0005] (3) Angle of resin, etc.: Patent CN114561097B discloses a colored weather-resistant glass fiber-reinforced polyamide composition and its preparation method and application. By forming a covalent bond network using an ionomer, polyamide 6 resin and organic toner, the migration of the organic toner is slowed down or restricted, so that the ability of the organic toner to change color under light is weakened, thereby improving the light aging and weather resistance of the colored glass fiber-reinforced polyamide composition. Patent CN112500700A discloses a blowable weather-resistant nylon composition and its preparation method. By introducing a compound system of Surlyn resin and titanium dioxide, the weather resistance of the nylon material is significantly improved. Patent CN116496619B discloses a red nylon composite material and its preparation method and application. Using a nylon resin with a specific viscosity as the matrix and combining with the toner bis(p-chlorophenyl)-1,4-diketopyrrolo[3,4-c]pyrrole to improve the dispersion uniformity of the toner in the nylon resin, so as to improve the coloring uniformity, and matching with a specific type of nucleating agent to change the homogeneous nucleation of the nylon resin into heterogeneous nucleation, accelerating the crystallization rate of the nylon resin. The three act on each other, so as to improve the weather resistance of the composite material while maintaining good vividness.

[0006] When exposed to the outdoor natural environment, the material will be affected by various factors such as sunlight (ultraviolet rays), heat, oxygen, and water, resulting in consequences such as whitening, sticking, embrittlement, discoloration, cracking, and deterioration of mechanical properties. The molecular chains at the weak positions with defects such as stress and impurities in the surface layer of the polymer are the first to age and break, producing small molecule products, which fall off under the scouring of precipitation. Even more, nylon materials are easy to absorb water. Under the outdoor climate of day and night alternation, the repeated water absorption expansion and water loss contraction exacerbate the crack expansion and shedding. As the aging progresses, it gradually spreads from the surface to the inside of the composite material, further leading to a decline in mechanical properties.

[0007] In summary, the existing technologies mostly focus on color difference, and there are few research reports on changes such as gloss and cracking. Summary of the Invention

[0008] The purpose of the present invention is to provide a weather-resistant repair type polyamide composition, after outdoor weathering and aging, the changes in color difference and gloss are significantly reduced, and there is no stickiness, whitening or cracking.

[0009] The present invention adopts the following technical solutions:

[0010] A weather-resistant repair type polyamide composition, comprising the following raw materials in parts by weight:

[0011] 30-99 parts of polyamide resin;

[0012] 0.5-5 parts of weather-resistant repair agent;

[0013] 0-50 parts of reinforcing material;

[0014] 0-30 parts of flame retardant;

[0015] 0-5 parts of color powder;

[0016] 1-5 parts of other additives;

[0017] Wherein the weather-resistant repair agent is a mineral inorganic gel coated with a silane coupling agent.

[0018] The mineral inorganic gel includes natural and synthetic ones; preferably lithium magnesium silicate and magnesium aluminum silicate; wherein, the apparent viscosity (5% concentration) of the mineral inorganic gel ≥ 1000 mPa·s; more preferably ≥ 2000 mPa·s; wherein, from the perspective of the mechanical properties of the composition and the convenience of coating treatment, the size of the above-mentioned mineral inorganic gel is preferably 500-5000 mesh; wherein, from the perspective of convenient color matching of the product, the whiteness of the above-mentioned mineral inorganic gel is preferably > 80.

[0019] The molecular structural formula of the silane coupling agent is generally Y-R-Si(OR)3 (where Y: organic functional group; SiOR: silane oxy group). The silane coupling agent is used for microcapsule coating treatment of the mineral inorganic gel; wherein, from the perspective of sealing and waterproofing, the mass of the above-mentioned silane coupling agent is more than 5% of the mass of the mineral inorganic gel; more preferably, the mass of the silane coupling agent is 5%-15% of the mass of the mineral inorganic gel.

[0020] The polyamide resin is selected from at least one of PA6, PA56, PA66, and PA6 / 66.

[0021] The reinforcing material is selected from one or more of glass fiber, basalt fiber, wollastonite, potassium titanate whisker, mica, and diatomite in fibrous, sheet-like or powdery form.

[0022] The flame retardant is selected from decabromodiphenylethane, brominated polystyrene, polybrominated styrene, red phosphorus, black phosphorus, melamine cyanurate, melamine polyphosphate, aluminum diethylphosphinate, aluminum polyphosphite, zinc stannate, zinc borate, antimony trioxide, etc.

[0023] The color powder is selected from inorganic pigments, organic pigments, dyes, etc.; from the perspective of outdoor weather resistance applications, inorganic pigments are preferred.

[0024] The other additives also include conventional processing aids, including one or several mixtures of antioxidants, lubricants, mold release agents, nucleating agents, light stabilizers, and toughening agents.

[0025] The preparation method of the above weather-resistant repair type polyamide composition is as follows:

[0026] (1) Weigh each raw material according to the formula; (2) Put other components except glass fiber into a high-speed mixer and mix until uniform to obtain a premix; (3) Then put the obtained premix into a twin-screw extruder for melt mixing, and the fiber-reinforced filler adopts a side feeding process for extrusion granulation to obtain the composition; the extrusion temperature is 230 - 280 °C, and the screw speed is set at 480 - 600 rpm.

[0027] The mechanism of the weather-resistant repair of the present invention is as follows: Under the action of various factors such as sunlight, heat, oxygen, and water, when microcracks begin to appear on the surface layer of the polyamide composition, the microcapsule shell layer of the silane coupling agent at the position of the microcracks is damaged, and the exposed mineral inorganic gel contacts water and begins to play the role of hydrated gel. At the microcracks, with the help of the anchor points at the crack interface, the water-inorganic colloid network structure with high transparency and high viscoelasticity has good suspension stability, can effectively fill the microcracks, resist spray scouring, and prevent the expansion of microcracks, achieving the effect of gel plugging and repair.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) The present invention adopts the principle of hydrated gel. When microcracks appear on the surface of the composition, the exposed mineral inorganic gel reacts with water to generate an inorganic colloid with high transparency and high viscoelasticity, filling the microcracks, resisting spray scouring, and preventing the expansion of microcracks, achieving the effect of gel plugging and repair;

[0030] 2) The present invention coats and treats the mineral inorganic gel with a silane coupling agent to form a microcapsule silane shell, which not only optimizes the dispersion distribution and does not affect the mechanical properties; but also plays a role in slow release of the effect. Only after the microcapsule is damaged, the exposed mineral inorganic gel contacts water and begins to play the role of hydrated gel; ensuring that the mineral inorganic gel does not exude and become sticky on the non-damaged surface;

[0031] 3) The present invention can enhance the weather resistance and maintain the glossiness of the surface by preventing the expansion of microcracks and sealing and repairing the cracks. It is not affected by color matching and formulation systems and is applicable to the applications of colored, flame-retardant and other products. Description of the Drawings

[0032] Figure 1 It is the visual and microscopic magnified "normal" photo of Example 3 of the present invention;

[0033] Figure 2 It is the visual "whitening" and microscopic magnified "cracking" photos of Comparative Example 8 of the present invention;

[0034] Figure 3 It is the microscopic magnified "whitening and cracking" photo of Comparative Example 6 of the present invention; Detailed Embodiments

[0035] To make the technical solutions of the present invention clearer and more definite, the present invention will be further described below. Any solutions obtained by equivalent replacement of the technical features of the technical solutions of the present invention and through conventional reasoning fall within the protection scope of the present invention.

[0036] The materials used in the present invention are as follows:

[0037] PA6: M2400

[0038] PA66: EPR27

[0039] Weather resistance repair agent 1: Lithium magnesium silicate, viscosity 2500 mPa·s, silane coupling agent coating amount 6%;

[0040] Weather resistance repair agent 2: Lithium magnesium silicate, viscosity 1500 mPa·s, silane coupling agent coating amount 15%;

[0041] Weather resistance repair agent 3: Magnesium aluminum silicate, viscosity 2500 mPa·s, silane coupling agent coating amount 10%;

[0042] Weather resistance repair agent 4: Magnesium aluminum silicate, viscosity 2500 mPa·s, silane coupling agent coating amount 1%;

[0043] Weather resistance repair agent 5: Lithium magnesium silicate, viscosity 800 mPa·s, silane coupling agent coating amount 15%;

[0044] Weather resistance repair agent 6: Lithium magnesium silicate, viscosity 2500 mPa·s, silane coupling agent coating amount 30%;

[0045] Glass fiber: 301HP

[0046] Wollastonite: TH-108

[0047] Lubricant: A-C540A

[0048] Light stabilizer 1: Tinuvin-234

[0049] Light stabilizer 2: Chimassorb 944

[0050] Antioxidant 1: Irganox 1098

[0051] Antioxidant 2: Irganox 168

[0052] Color powder package: self-made

[0053] Weigh the reinforcing material, filler, nylon resin, lubricant, antioxidant, light stabilizer and color powder package respectively according to the specific examples described in Table 1 and the formulation dosages (parts by weight) of the comparative examples in Table 2. Put the other components except glass fiber into a high-speed mixer and mix until uniform to obtain a premix; then put the obtained premix into a twin-screw extruder for melt mixing. The fiber-reinforced filler adopts the side feeding process for extrusion granulation to obtain the composition; the extrusion temperature is 230-280 °C, and the screw speed is set at 480-600 rpm.

[0054] Performance test method:

[0055] Tensile strength: According to ISO 527 method, the specimen size is 170*10*4 mm, and the test speed is 5 mm / min;

[0056] Flexural strength: According to ISO 178 method, the specimen size is 80*10*4 mm, and the test speed is 5 mm / min;

[0057] Izod impact strength: According to ISO 179 / 1eA method, the specimen size is 80*10*4 mm;

[0058] Color change: The specimen size is 70*50*3 mm. Using the SAE J2527 automotive exterior method, evaluate the color difference △E before and after 1500 h;

[0059] Gloss change: The specimen size is 70*50*3 mm. Using the SAE J2527 automotive exterior method, evaluate the difference in gloss △G before and after 1500 h;

[0060] Appearance evaluation: The specimen size is 70*50*3 mm. Using the SAE J2527 automotive exterior method, visually observe, magnify 50 times with a microscope, and touch and evaluate the appearance change after 1500 h.

[0061] Table 1 Component ratios (parts by weight) of each example and the results of each performance test

[0062]

[0063]

[0064] Table 2 Component ratios (parts by weight) of each group in the comparative examples and the test results of each performance

[0065]

[0066] It can be seen from the data shown in the table that after being treated by the SAE J2527 automotive exterior trim method for 1500 h, the change in color difference and gloss of the present invention is significantly reduced, and both can meet ≥ level 4 according to the gray scale rating, and the technical effect is remarkable. The coating amount of the silane coupling agent and the apparent viscosity of the mineral inorganic gel directly affect whether the weather resistance repair agent can function (Comparative Examples 1, 2, 3, 7). Examples beyond the reasonable range of the present invention will have negative impacts such as influencing mechanical properties, stickiness, whitening, and cracking.

Claims

1. A weather-resistant repairable polyamide composition, characterized in that: The invention comprises the following raw materials in parts by weight: The weather-resistant repair agent is a mineral inorganic gel coated with a silane coupling agent.

2. A weather-resistant and repairable polyamide composition according to claim 1, characterized in that: The mineral inorganic gel includes natural and artificially synthesized lithium magnesium silicate and aluminum magnesium silicate; wherein the apparent viscosity of the mineral inorganic gel is ≥1000mPa.s.

3. A weather-resistant and repairable polyamide composition according to claim 2, characterized in that: The apparent viscosity of the mineral inorganic gel is ≥2000mPa.s; from the perspective of mechanical properties of the composition and convenience of coating treatment, the size of the mineral inorganic gel is 500-5000 mesh; wherein, from the perspective of convenient product color matching, the whiteness of the mineral inorganic gel is preferably >80.

4. The weather-resistant and repairable polyamide composition according to claim 1, characterized in that: The molecular structural formula of the silane coupling agent is YR-Si(OR)3, wherein Y is an organic functional group and SiOR is a silaneoxy group. The silane coupling agent is used to microencapsulate the mineral inorganic gel. From the perspective of sealing and waterproofing, the mass of the silane coupling agent is more than 5% of the mass of the mineral inorganic gel.

5. A weather-resistant and repairable polyamide composition according to claim 4, characterized in that: The mass of the silane coupling agent is 5%-15% of the mass of the mineral inorganic gel.

6. The weather-resistant and repairable polyamide composition according to claim 1, characterized in that: The polyamide resin is selected from at least one of PA6, PA56, PA66 and PA6 / 66.

7. The weather-resistant and repairable polyamide composition according to claim 1, characterized in that: The reinforcing material is selected from one or more of glass fiber, basalt fiber, wollastonite, potassium titanate whisker, mica, diatomaceous earth in fibrous, flaky or powdery form.

8. The weather-resistant and repairable polyamide composition according to claim 1, characterized in that: The flame retardant is selected from decabromodiphenylethane, brominated polystyrene, polybrominated styrene, red phosphorus, black phosphorus, melamine cyanurate, melamine polyphosphate, diethyl aluminum hypophosphite, polyaluminum phosphite, zinc stannate, zinc borate, and antimony trioxide.

9. The weather-resistant and repairable polyamide composition according to claim 1, characterized in that: The color powder is selected from inorganic pigments, organic pigments, and dyes; the other additives also include one or a mixture of antioxidants, lubricants, release agents, nucleating agents, light stabilizers, and toughening agents.

10. The method for preparing the weather-resistant and repairable polyamide composition according to any one of claims 1 to 9, characterized in that: The steps are as follows: (1) weighing each raw material according to the amount of the formula; (2) putting all the components except the glass fiber into a high-speed mixer and mixing them until they are uniform to obtain a premix; (3) then putting the obtained premix into a twin-screw extruder for melt mixing, and the fiber-reinforced filler is extruded and granulated by a side feeding process to obtain a composite; The extrusion temperature is 230-280°C, and the screw speed is set to 480-600rpm.

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