Coloring treatment process of ultraviolet-proof polyurethane pultruded profile

Abstract

The invention relates to the technical field of coloring treatment, in particular to a coloring treatment process of an ultraviolet-proof polyurethane pultruded profile, which comprises the following steps: firstly, carrying out surface cleaning and chemical activation pretreatment on a polyurethane pultruded profile matrix; then preparing functional slurry containing a coloring agent, an ultraviolet light absorber and a hindered amine light stabilizer; then, the pretreated profile is soaked in the functional slurry under the vacuum or pressure condition, so that the functional slurry permeates to the surface layer of the profile; then carrying out pre-curing treatment to form a functional transition layer; then coating a transparent polyurethane outer protective layer on the functional transition layer; and finally, cross-linking is completed through stepped heating curing. According to the invention, the integration of coloring and anti-ultraviolet functions is realized through the vacuum impregnation process, the adhesive force, color durability and weather resistance of the coating are improved, and the problems that the coating is easy to peel off and the protection effect is not lasting in the traditional process are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coloring treatment, in particular to a coloring treatment process of a polyurethane pultruded profile capable of preventing ultraviolet rays. BACKGROUND

[0002] Polyurethane pultruded profiles have been widely used in the fields of construction, transportation and outdoor facilities due to their excellent strength-to-weight ratio, corrosion resistance and design flexibility. However, when the profiles are exposed to outdoor environments for a long time, especially under strong ultraviolet radiation, the polymer molecular chains are prone to photo-oxidative degradation, resulting in powdering, discoloration, gloss reduction and even mechanical property degradation on the surface of the material, which seriously affects the appearance life and use safety of the product.

[0003] In order to improve the weather resistance of polyurethane profiles and impart color, the existing technology mainly adopts two approaches: one is to directly add color paste and ultraviolet-resistant additives to the base resin, and the other is to perform surface spraying or film coating on the formed profile.

[0004] In the first method, the addition of color paste and additives may interfere with the stability of the pultrusion process, affect the curing of the resin, and the pigment and additives may not be uniformly dispersed in the matrix or may migrate later, affecting the effect; the second treatment method has the problem of insufficient adhesion between the coating and the polyurethane substrate, which is prone to peeling and peeling under thermal stress or mechanical stress; at the same time, a single coating structure often cannot balance the bright and durable coloring and long-term ultraviolet resistance performance, and its protective effect is limited and not durable. SUMMARY

[0005] The present application aims to provide a coloring treatment process for a polyurethane pultruded profile capable of preventing ultraviolet rays, which solves the technical problems of difficulty in integrating coloring function and ultraviolet resistance function in the prior art, and insufficient adhesion between the coating and the matrix, resulting in a non-durable protective effect.

[0006] To achieve the above-mentioned purpose, the present application provides a coloring treatment process for a polyurethane pultruded profile capable of preventing ultraviolet rays, comprising the following steps: The surface of the polyurethane pultruded profile matrix is pretreated, and the pretreatment includes cleaning and chemical activation; A colored ultraviolet-resistant functional slurry is prepared, which comprises a polyurethane resin base liquid, a colorant, and a composite ultraviolet stabilizer composed of an ultraviolet absorber and a hindered amine light stabilizer; The pretreated profile is immersed in the functional slurry in a closed environment under vacuum or pressure conditions, so that the slurry penetrates into the surface layer of the profile; The immersed profile is subjected to pre-curing treatment to form a functional transition layer on the surface of the profile; A transparent polyurethane outer protective layer is coated on the functional transition layer; The profile coated with the outer protective layer is subjected to stepwise temperature curing, preliminary curing at a first temperature, and final cross-linking curing at a higher second temperature.

[0007] The specific steps of the surface pretreatment of the polyurethane pultrusion profile substrate include: The profile surface is wiped or rinsed with an organic solvent to remove oil stains and residual release agent. The cleaned profile is immersed in a dilute solution of silane coupling agent, or the silane coupling agent dilute solution is coated on the profile surface by spraying. The treated profile is subjected to preliminary drying to form an activated layer of the coupling agent on the profile surface.

[0008] The specific steps of preparing the colored anti-ultraviolet functional slurry include: The following components are prepared by weight parts: polyurethane resin base fluid 100 parts, colorant 1-10 parts, benzotriazole ultraviolet absorber 0.5-5 parts, and hindered amine light stabilizer 0.2-3 parts. The polyurethane resin base fluid, colorant, ultraviolet absorber, and light stabilizer are added to a stirred tank and preliminarily mixed uniformly under low-speed stirring. The preliminarily mixed slurry is transferred to a three-roll mill or basket mill for cyclic grinding until the slurry fineness is not greater than 25 μm as indicated by sampling detection.

[0009] The specific steps of placing the pretreated profile in a sealed environment, immersing it in the functional slurry under vacuum or pressure conditions, and allowing the slurry to penetrate the profile surface layer include: The profile is completely immersed in the immersion tank containing the functional slurry and sealed. The vacuum system is started, and the pressure in the immersion tank is reduced to a negative pressure state of -0.05 to -0.08 MPa. The vacuum pressure is maintained, and the profile is immersed in the slurry for 5-30 minutes. The immersion tank is slowly returned to normal pressure, the profile is smoothly taken out of the slurry, and the excess slurry on the surface is drained to form a uniform wet film.

[0010] The specific steps of the pre-curing treatment of the immersed profile include: The pre-curing treatment is performed in a forced air drying oven or a tunnel type curing oven, and the curing conditions are 60-80℃ for 10-30 minutes.

[0011] Before coating the transparent polyurethane outer protective layer on the functional transition layer, a step of adjusting the protective liquid is included, which comprises: Add 1% to 5% of nano-silica particles by weight to the transparent polyurethane resin, and stir for 10 to 30 minutes by a high-speed shearing dispersion machine to uniformly disperse the nano-particles in the resin.

[0012] The specific steps of preliminary curing at the first temperature and final cross-linking curing at the second higher temperature include: Send the profile into the first-stage curing zone, and cure for 10 to 15 minutes in a circulating hot air environment at 80 to 90 DEG C to preliminarily shape the outer protective layer; Subsequently, transfer the profile into the second-stage curing zone, and perform cross-linking curing for 5 to 8 minutes in an infrared radiation or high-temperature hot air environment at 120 to 140 DEG C to promote the formation of firm chemical bonding between the functional transition layer and the outer protective layer.

[0013] The coloring treatment process of the ultraviolet-proof polyurethane pultruded profile of the present application realizes the integration of coloring function and ultraviolet-proof function by vacuum impregnation process to penetrate the functional slurry containing coloring and ultraviolet-proof components into the surface layer of the profile to form a transition layer, solves the problem of easy peeling of the traditional surface coating; the composite formula and composite structure of ultraviolet absorber plus hindered amine light stabilizer improve the weather resistance and service life of the product; the firm chemical bonding between the matrix and the coating is formed by surface chemical activation and stepwise temperature rising curing, ensuring the stability of the whole coating system; the wear resistance and ultraviolet-proof ability of the coating are further enhanced by adding nano-silica particles in the outer protective layer. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced.

[0015] Figure 1 is the flow chart of the coloring treatment process of the ultraviolet-proof polyurethane pultruded profile of the present application. DETAILED DESCRIPTION

[0016] The embodiments of the present application will be described in detail below, and the examples of the embodiments are shown in the drawings, the embodiments described below by referring to the drawings are exemplary, and are intended to explain the present application, and cannot be understood as the limitation of the present application.

[0017] Please refer to Figure 1 , wherein Figure 1 is the flow chart of the coloring treatment process of the ultraviolet-proof polyurethane pultruded profile of the present application.

[0018] The present application provides a coloring treatment process of an ultraviolet-proof polyurethane pultruded profile, including the following steps: S1: Surface pretreatment of the polyurethane pultruded profile substrate, the pretreatment including cleaning and chemical activation.

[0019] Specifically, S11: Wiping or rinsing the profile surface with an organic solvent to remove oil stains and residual release agent; S12: Immersing the cleaned profile in a dilute solution of silane coupling agent, or coating the profile surface with the dilute solution of silane coupling agent using a spraying method; S13: Preliminary drying of the treated profile to form an activated layer of coupling agent on the profile surface.

[0020] In the present embodiment, the organic solvent is preferably at least one of acetone, isopropyl alcohol or ethanol, with a purity of not less than 99% to ensure effective removal of surface contaminants without leaving impurities; the dilute solution of silane coupling agent is selected from γ-aminopropyl triethoxysilane (KH-550) or γ-(2,3-epoxypropoxy) propyl trimethoxysilane (KH-560), with a mixed solution of ethanol and deionized water (volume ratio 8:2) as the diluent, and the mass concentration of silane coupling agent in the mixed solution being 1.5% to 3%; when using a spraying method, the spraying pressure is controlled at 0.3 to 0.5 MPa, and the distance between the nozzle and the profile surface is maintained at 20 to 30 cm to ensure uniform atomization and coverage of the solution; preliminary drying is carried out in a circulating air oven at 50 to 65°C, with a drying time of 8 to 15 minutes, finally forming a complete and continuous layer of silane coupling agent molecules on the profile surface with high reactivity, which not only increases the surface energy but also creates conditions for subsequent infiltration and chemical bonding of functional slurry.

[0021] S2: Preparation of colored anti-ultraviolet functional slurry, the functional slurry comprising polyurethane resin base fluid, colorant and composite ultraviolet stabilizer composed of ultraviolet absorber and hindered amine light stabilizer.

[0022] Specifically, S21: Preparing the following components by weight parts: polyurethane resin base fluid 100 parts, colorant 1 to 10 parts, benzotriazole ultraviolet absorber 0.5 to 5 parts, and hindered amine light stabilizer 0.2 to 3 parts; S22: Pouring the polyurethane resin base fluid, colorant, ultraviolet absorber and light stabilizer into a stirred tank and mixing uniformly under low-speed stirring; S23: Transferring the preliminarily mixed slurry to a three-roll mill or basket mill for cyclic grinding until the slurry fineness is not greater than 25 μm as indicated by sampling and testing.

[0023] In the present embodiment, the polyurethane resin base fluid is preferably a two-component aliphatic polyurethane system, wherein the hydroxyl component is an acrylic modified polyurethane resin with a solid content of 60±2%; the colorant includes at least one of inorganic pigments and organic dyes, wherein the inorganic pigments are preferably rutile titanium dioxide and iron oxide pigments, and the organic dyes are preferably phthalocyanine blue and permanent red, and all colorants are filtered through a 1250 mesh screen to ensure no caking; the benzotriazole ultraviolet absorber is selected from UV-327 or UV-328, with a maximum absorption wavelength range of 300-380 nm; the hindered amine light stabilizer is selected from Tinuvin 292 or Tinuvin 770, which forms a synergistic stabilizing system with the ultraviolet absorber; in the stirring and mixing stage, the stirring tank speed is controlled at 300-500 rpm, and the mixing time is 30-45 minutes to ensure uniform dispersion of each component; in the grinding stage, the roll gap of the three-roll grinder is set to 10-15 μm, or the basket grinder uses 0.3-0.5 mm zirconium oxide beads as the grinding medium, and the slurry is ground to a fineness of 20±5 μm, and the slurry viscosity is controlled at 1500-2500 cps (25°C); the prepared functional slurry not only has excellent color strength and dispersion stability, but also has a broad spectrum of ultraviolet absorption and protection by the composite ultraviolet stabilizing system.

[0024] S3: The pretreated profile is placed in a closed environment and immersed in the functional slurry under vacuum or pressure conditions, allowing the slurry to penetrate the surface layer of the profile.

[0025] Specifically, S31: The profile is completely immersed in the immersion tank containing the functional slurry and sealed; S32: Start the vacuum system and reduce the pressure in the immersion tank to a negative pressure state of -0.05 ~ -0.08 MPa; S33: Maintain the vacuum pressure and allow the profile to stand in the slurry for 5-30 minutes; S34: Slowly restore the immersion tank to normal pressure, smoothly remove the profile from the slurry, and drain the excess slurry on the surface to form a uniform wet film.

[0026] In the present embodiment, the impregnation tank is made of stainless steel and is equipped with a jacket temperature control system, which can maintain the slurry temperature at 25±2℃ during the impregnation process; during the pressure-keeping impregnation stage, the pressure change in the tank is recorded by a real-time monitoring system, if the pressure rises more than 0.005 MPa within 5 minutes, the vacuum is re-pumped to the set value; the recovery of normal pressure process adopts a segmented control, first the pressure is recovered to-0.02 MPa within 2-3 minutes, and then completely recovered to normal pressure after 1 minute, which can effectively avoid the boiling of slurry or surface defects of the profile caused by sudden pressure change; when draining the excess slurry, the profile is hung on a special draining rack at an inclination angle of 15-20°, and is placed in a clean environment with a relative humidity of ≤40% for 5-8 minutes until a wet film with uniform thickness and no dripping is formed on the surface, and the thickness is controlled within the range of 80-120 μm.

[0027] S4: Pre-curing treatment is performed on the impregnated profile to form a functional transition layer on the surface of the profile.

[0028] Specifically, the pre-curing treatment is performed in a forced air drying oven or a tunnel type curing oven, and the curing conditions are as follows: temperature of 60-80℃, and holding time of 10-30 minutes.

[0029] In the present embodiment, the pre-curing treatment is performed in a bridge type curing oven, and the temperature uniformity in the oven is controlled within ±2℃; the pre-curing process adopts a stepwise temperature rising program: first, the slurry is dried on the surface at 60℃ for 5-8 minutes, then the temperature is raised to 70-80℃ for 15-25 minutes to complete the drying; the relative humidity in the oven is controlled within the range of 40-50% to prevent pinhole or bubble defects on the surface of the coating; the profile is hung in the curing oven during the pre-curing process to ensure uniform heating of all surfaces, and the conveying belt speed is controlled at 0.8-1.2 m / min; the functional transition layer formed after pre-curing has a thickness of 50-80 μm, the adhesion to the substrate reaches level 1, and a stable three-dimensional cross-linked network structure is formed inside the transition layer, providing ideal interface conditions for the subsequent coating of the outer protective layer; the functional transition layer firmly fixes the colorant and ultraviolet stabilizer, and its micro-porous structure also creates conditions for the penetration and anchoring of the outer protective layer.

[0030] S5: Coating a transparent polyurethane outer protective layer on the functional transition layer.

[0031] Specifically, before coating the transparent polyurethane outer protective layer, the protective liquid is prepared, and the preparation steps include: 1% to 5% of nano-silicon dioxide particles by weight are added to the transparent polyurethane resin, and stirred for 10-30 minutes by a high-speed shearing disperser to uniformly disperse the nano-particles in the resin.

[0032] In the embodiment, the nanosilica particles are dried at 120℃ for 2 hours before use to remove adsorbed moisture; the transparent polyurethane resin is selected from an aliphatic polyurethane system; during dispersion, the rotational speed of the high-speed shearing disperser is set to 3000-5000 rpm, the dispersion time is 15-25 minutes, and the nanosilica powder is added in three portions during the dispersion process, with an interval of 5 minutes between each addition, to ensure that the particles are fully wetted and dispersed; after dispersion is complete, the dispersion state of the nanoparticles in the slurry is detected using a laser particle size analyzer; the viscosity of the prepared protective liquid is controlled to 1500-2000 cps (25℃), the solid content is 55±2%, and the protective liquid is used up within 4 hours to prevent the nanoparticles from settling and the resin viscosity from changing; the protective liquid not only maintains excellent transparency, but also improves the wear resistance, scratch resistance, and ultraviolet resistance of the outer protective layer due to the introduction of nanosilica.

[0033] S6: The profile coated with the outer protective layer is subjected to stepwise temperature curing, first preliminary curing at a first temperature, and then final crosslinking curing at a higher second temperature.

[0034] Specifically, S61: The profile is sent to the first-stage curing zone and cured in a circulating hot air environment at 80-90℃ for 10-15 minutes to preliminarily set the outer protective layer; S62: Subsequently, the profile is transferred to the second-stage curing zone and subjected to crosslinking curing in an infrared radiation or high-temperature hot air environment at 120-140℃ for 5-8 minutes to promote the formation of firm chemical bonding between the functional transition layer and the outer protective layer.

[0035] In the embodiment, the first-stage curing zone uses a bridge-type hot air circulating curing furnace, and the hot air circulation speed is controlled to 8-10 m / s; the second-stage curing zone is equipped with a medium-wave infrared radiation system, which has a wavelength range of 2.5-3.5 μm and matches the absorption peaks of functional groups such as N-H and C=O in the polyurethane molecules; during the first-stage curing process, the furnace is kept at a slight positive pressure to prevent external pollutants from entering; during the second-stage curing, the infrared radiation intensity is controlled to 8-12 kW / m 2 , the distance between the radiation plate and the profile surface is kept at 30-50 cm, and the profile surface temperature is monitored in real time by an infrared thermometer to ensure that the temperature is controlled within the set range; during the curing process, the profile is conveyed by a variable frequency speed transmission system; after stepwise curing, firm chemical bonding is formed between the outer protective layer and the functional transition layer, and the coating surface hardness reaches 3H (GB / T 6739-2006); this stepwise temperature curing process not only ensures the full crosslinking of the coating, but also avoids defects in the coating caused by rapid temperature changes.

[0036] The coloring treatment process of the ultraviolet-proof polyurethane pultrusion profile of the application solves the technical problem of easy peeling of the traditional coating by combining surface chemical activation and vacuum impregnation process, so that the functional slurry fully penetrates into the profile surface layer to form a functional transition layer chemically bonded with the matrix, and then realizes the fusion of the three-layer structure through step curing, and adopts the composite formula and composite structure of ultraviolet absorber and hindered amine light stabilizer to form multiple protection, which not only ensures the persistent bright color, but also significantly improves the overall weather resistance.

[0037] The above only discloses one or more preferred embodiments of the application, and cannot limit the scope of the application. Those skilled in the art can understand that the implementation of all or part of the above-mentioned embodiments is still within the scope of the application.

Claims

1. A coloring process of a UV-resistant polyurethane pultrusion profile, characterized by, The method comprises the following steps: Surface pretreatment is performed on the polyurethane pultruded profile substrate, and the pretreatment comprises cleaning and chemical activation; A colored anti-ultraviolet functional slurry is prepared, and the functional slurry comprises a polyurethane resin base liquid, a colorant, and a composite ultraviolet stabilizer composed of an ultraviolet absorber and a hindered amine light stabilizer; The pretreated profile is immersed in the functional slurry in a closed environment under vacuum or pressure conditions, so that the slurry penetrates into the surface layer of the profile; Pre-curing treatment is performed on the immersed profile to form a functional transition layer on the surface layer of the profile; A transparent polyurethane outer protective layer is coated on the functional transition layer; The profile coated with the outer protective layer is subjected to stepwise temperature curing, and preliminary curing is first performed at a first temperature, and then final crosslinking curing is completed at a second higher temperature.

2. The coloring process of the ultraviolet resistant polyurethane pultrusion profile according to claim 1, characterized in that, The specific steps of the surface pretreatment of the polyurethane pultruded profile substrate comprise: The surface of the profile is wiped or washed with an organic solvent to remove oil stains and residual release agents; The cleaned profile is immersed in a dilute solution of a silane coupling agent, or the dilute solution of the silane coupling agent is coated on the surface of the profile by spraying; The treated profile is subjected to preliminary drying, so that the coupling agent forms an activated layer on the surface of the profile.

3. The coloring process of the ultraviolet resistant polyurethane pultrusion profile according to claim 1, characterized in that, The specific steps of the preparation of the colored anti-ultraviolet functional slurry comprise: The following components are prepared by weight parts: 100 parts of a polyurethane resin base liquid, 1 to 10 parts of a colorant, 0.5 to 5 parts of a benzotriazole ultraviolet absorber, and 0.2 to 3 parts of a hindered amine light stabilizer; The polyurethane resin base liquid, the colorant, the ultraviolet absorber, and the light stabilizer are put into a stirring kettle, and are preliminarily mixed uniformly under low-speed stirring; The preliminarily mixed slurry is transferred to a three-roll grinding machine or a basket grinding machine, and is subjected to cyclic grinding until the slurry fineness is not greater than 25 μm as indicated by sampling detection.

4. The coloring process of the ultraviolet resistant polyurethane pultrusion profile according to claim 1, characterized in that, The specific steps of the immersion of the pretreated profile in the functional slurry in a closed environment under vacuum or pressure conditions, so that the slurry penetrates into the surface layer of the profile, comprise: The profile is completely immersed in an immersion tank containing the functional slurry and is sealed; A vacuum system is started, and the pressure in the immersion tank is reduced to a negative pressure state of -0.05 to -0.08 MPa; The vacuum pressure is maintained, and the profile is allowed to stand and immerse in the slurry for 5 to 30 minutes; The immersion tank is slowly restored to normal pressure, the profile is smoothly taken out of the slurry, and the excess slurry on the surface is drained to form a uniform wet film.

5. The coloring process of the ultraviolet resistant polyurethane pultrusion profile according to claim 1, characterized in that, The specific steps of the pre-curing treatment of the immersed profile comprise: The pre-curing treatment is performed in a forced air drying oven or a tunnel type curing oven, and the curing conditions are that the temperature is 60 to 80 ℃, and the time is 10 to 30 minutes.

6. The coloring process of the ultraviolet resistant polyurethane pultrusion profile according to claim 1, wherein, Before the transparent polyurethane outer protective layer is coated on the functional transition layer, a step of adjusting the protective liquid is further included, and the step comprises: 1% to 5% of nano silicon dioxide particles by weight are added to the transparent polyurethane resin, and the nano particles are uniformly dispersed in the resin by stirring for 10 to 30 minutes through a high-speed shearing dispersion machine.

7. The coloring process of the ultraviolet resistant polyurethane pultrusion profile according to claim 1, characterized by, The specific steps of the preliminary curing at a first temperature and the final crosslinking curing at a second higher temperature comprise: The profile is sent into the first stage curing area, and cured in the circulating hot air environment of 80-90℃ for 10-15 minutes to preliminarily shape the outer protective layer; Then the profile is transferred to the second stage curing area, and cross-linked cured in the infrared radiation or high temperature hot air environment of 120-140℃ for 5-8 minutes to form firm chemical bonding between the functional transition layer and the outer protective layer.

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