Heat vulcanization repairing method for surface color difference of light-color rubber product

Abstract

The invention provides a heat vulcanization repair method for color difference on the surface of a light-color rubber product. The heat vulcanization repair method comprises the following steps: a) polishing, decontaminating and drying a target surface with color difference; b) preparing a repairing sheet by adopting an unvulcanized rubber compound which is consistent with the formula of the light-color rubber plate matrix, and enabling the repairing sheet to cover the color difference area and be matched with the color difference area in shape; c) respectively coating the surface of the color difference area and the to-be-laminated surface of the repairing sheet with a hot vulcanization adhesive, and airing until the surfaces are dry; d) the repairing sheet and the color difference area are aligned, attached and pre-compacted; e) carrying out heat vulcanization on the attached part under the pressurizing and heating conditions; through the same-formula unvulcanized repairing sheet and two pressurization heat vulcanization processes of mold pressing / air inflation, effective shielding of color difference on the surface of the light-color rubber plate and reliable bonding of an interface are achieved, appearance consistency and size keeping are both considered, and the method is suitable for repairing planar and curved-surface products.

Description

Technical Field

[0001] This invention belongs to the field of rubber repair technology, specifically relating to a hot vulcanization repair method for color difference on the surface of light-colored rubber products. Background Technology

[0002] Light-colored rubber sheets (including light-colored rubber products) are prone to surface color differences after vulcanization. A common cause of color difference is uneven dispersion of compounding agents during the mixing stage, leading to non-uniform discoloration under heat and pressure during vulcanization. For light-colored products, visually perceptible color differences are generally unacceptable to customers and are considered significant appearance defects.

[0003] Current repair methods mostly involve locally or entirely grinding the defective area according to the severity of the color difference in order to remove the surface color difference. However, this method is not always effective, easily damages the surface of the product, resulting in uneven color, an uneven appearance, or even scrapping the product. The pass rate after repair fluctuates greatly and is uncontrollable, usually not exceeding 50%. These problems make it difficult for existing processes to achieve stable and reproducible repair results while ensuring appearance quality.

[0004] Therefore, there is an urgent need for a light-colored rubber sheet surface color difference repair technology that can effectively mask color differences and maintain stable repair quality and pass rate without damaging the appearance and size of the product. Summary of the Invention

[0005] This invention provides a heat vulcanization repair method for color difference on the surface of light-colored rubber products, solving the problems existing in the prior art.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for heat vulcanization repair of color differences on the surface of light-colored rubber products, characterized in that it includes:

[0008] a) Polish, clean, and dry the target surface where there is a color difference;

[0009] b) Prepare a repair sheet using an unvulcanized compound rubber with the same formulation as the light-colored rubber sheet matrix, so that the repair sheet covers the color difference area and matches its shape;

[0010] c) Apply hot-curing adhesive to the surface of the color difference area and the surface of the repair sheet to be bonded, respectively, and let them dry until surface dry;

[0011] d) Align and bond the repair sheet with the color difference area and pre-press it;

[0012] e) The bonding area is subjected to thermal vulcanization under pressure and heating conditions, wherein the pressure is applied by one of the following two methods:

[0013] e1) Place the laminated light-colored rubber sheet into its molding mold, close the mold, apply pressure, and then heat-vulcanize; or

[0014] e2) An elastic air bladder is provided on the outside of the fitting part and then inflated and pressurized before hot vulcanization.

[0015] Furthermore, the pressurization method involves placing the bonded light-colored rubber sheet into its original molding mold for mold closing, pressurization, and hot vulcanization.

[0016] Furthermore, the pressurization method involves setting an elastic air bladder on the outside of the bonding area and inflating it to apply pressure, so that the elastic air bladder provides uniform surface pressure to the bonding interface before hot vulcanization.

[0017] Furthermore, a heat-resistant insulating release layer is provided between the elastic inflatable bladder and the repair sheet to facilitate removal after thermal vulcanization.

[0018] Furthermore, thermal vulcanization is carried out in an external heating environment to ensure that the bonding interface reaches the vulcanization temperature of the rubber compound.

[0019] Furthermore, the thermal vulcanization conditions are: temperature 160℃±5℃, time 40min±5min, and vulcanization pressure 11~15MPa.

[0020] Furthermore, during the mold closing process, excess repair material overflows along the parting surface, forming a peelable thin flash.

[0021] Furthermore, the thickness of the repair sheet is 0.1 to 0.5 mm.

[0022] Furthermore, the repair sheet is prepared into a sheet shape by a rubber calender and then cut according to the shape of the color difference area.

[0023] Furthermore, in step a), the surface treatment involves manual or mechanical sanding with sandpaper to remove surface deposits and aging layers. After sanding, the surface is wiped with anhydrous ethanol and allowed to air dry. In step c), the hot vulcanizing adhesive is applied in two coats and allowed to dry to surface dry before bonding.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention involves bonding an uncured repair sheet with the same formulation as the substrate to the area of ​​color difference. The repair process is then completed within the original molding die, involving mold closing, pressure application, and hot vulcanization. Under temperature and pressure, the sheet undergoes viscoelastic flow, forming a covering film that effectively masks the original color difference. The repaired surface is uniform in color, flat, and smooth. This process relies on the original mold, facilitating process reproduction and integration with production cycles. The repaired samples exhibit flatness and no color difference in appearance, and the measured dimensions remain within the original design tolerances, ensuring both appearance quality and dimensional consistency. The interfacial bonding strength is reliable; the measured peel strength between the EPDM rubber compound and the vulcanized rubber is 1.8 kN / m, exceeding the 1.0 kN / m evaluation benchmark in the documentation. Overall, the process stability is improved, with the appearance and pass rate consistently maintained at approximately 90%. This method is applicable to both molded hot vulcanization repair of flat rubber sheets and bladder-type inflatable hot vulcanization repair of curved linings, demonstrating good applicability.

[0026] Of course, implementing the various technical solutions of this invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the surface color difference repair process of rubber products by molding and hot vulcanization in Example 1;

[0029] Figure 2 This is a schematic diagram of the gas-filled hot vulcanization repair process for color difference in curved rubber products in Example 2.

[0030] Figure 3 This is a schematic diagram of the color difference repair process for curved rubber products using gas-filled hot vulcanization, as shown in Example 2.

[0031] In the diagram, 1- rubber hot vulcanizing adhesive, 2- rubber product (already vulcanized), 3- rubber compound sheet, 4- upper mold of molding die, 5- lower mold of molding die. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0033] In the description of this patent, it should be understood that the terms “center,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this patent and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this patent.

[0034] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] Example 1:

[0036] A method for repairing color differences on the surface of light-colored rubber products using heat vulcanization, specifically a planar molding heat vulcanization repair method, includes the following steps:

[0037] S1 Specifications and Defect Confirmation: The product to be repaired is a 1000mm×600mm×2.2mm white EPDM rubber sheet; mark the boundaries of the color difference area and record the location.

[0038] S2 Surface Pretreatment: Use sandpaper (e.g., 120 grit) to manually or mechanically sand the surface with color difference to remove dust and oil; then clean with anhydrous ethanol and let it stand until the surface is dry.

[0039] S3 Repair Sheet Preparation and Cutting: Select white rubber compound with the same formula as the base material, and use a calender to prepare sheets with a thickness of 0.1-0.5mm; cut them by hand into 1000mm×450mm sheets for later use as needed for repair.

[0040] S4 Bonding Interface Treatment: Apply two coats of hot vulcanizing adhesive to both the surface to be repaired and the surface to be bonded with the repair sheet, and let them dry until surface dry.

[0041] S5 bonding and pre-pressing: Align and bond the repair patch to the surface to be repaired, press manually to make the interface flat, and pay attention to aligning the edges of the bonding areas.

[0042] S6 Molding and Hot Vulcanization: Place the composite product and the repair sheet into the rubber sheet molding mold, with the product on top and the sheet on the bottom; close the mold, apply pressure, and perform hot vulcanization according to the same procedure as the original product. Process conditions: 160℃±5℃, 40min±5min, 11~15MPa.

[0043] S7 Mechanism Explanation: Under the action of temperature and pressure, the repair sheet undergoes viscoelastic flow along the repaired surface and forms a bond with the substrate. Excess material overflows along the parting surface to form a very thin flash, which eventually covers the original color difference area, achieving a uniform, flat and smooth surface color.

[0044] S8 Inspection and Records: The appearance of the repaired sample was "flat and without color difference", and the dimensional measurements were within the nominal tolerance range; the peel strength test record of the ethylene propylene compound and the vulcanized rubber was 1.8 kN / m (evaluation benchmark ≥ 1.0 kN / m).

[0045] See Figure 1 In the cross-sectional structural diagram of the planar molding hot vulcanization repair process of the present invention: the rubber product (vulcanized) 2 is placed in the cavity of the lower mold 5 of the molding die, and its surface has color difference defects; the rubber compound sheet 3 with the same formula as the matrix is ​​attached to the color difference area. The rubber compound sheet 3 and the rubber product (vulcanized) 2, as well as the relative surfaces of the rubber compound sheet 3 and the upper mold 4, are bonded by the rubber hot vulcanization adhesive 1; the molding die is composed of the upper mold 4 and the lower mold 5. When the mold is closed, under the action of the external load P, the upper mold 4 is pressed down, so that the rubber compound sheet 3 generates viscoelastic flow under the combined action of temperature and pressure and is firmly vulcanized and bonded to the rubber product (vulcanized) 2. Excess rubber overflows along the parting surface to form a peelable flash, thereby completing the coverage and repair of the color difference area and obtaining a rubber sheet with uniform surface color, flat surface and consistent size.

[0046] Table 1. Actual Measured Dimensions of Repaired White EPDM Rubber Products

[0047]

[0048] This embodiment achieves color masking and consistent surface texture by using the same formula to repair thin sheets, the same mold surface pressure, and the same vulcanization method; the overall surface pressure of the mold cavity limits local thickening, thus balancing appearance and dimensional preservation.

[0049] Example 2:

[0050] See Figure 2 , Figure 3 A method for heat vulcanization repair of color differences on the surface of light-colored rubber products, specifically a curved bladder-type inflatable heat vulcanization repair method, includes the following steps:

[0051] S1 Defect Identification and Boundary Marking: Marking the boundaries of color difference areas on curved linings or arc-shaped products.

[0052] S2 Surface Pretreatment: The calibration area is uniformly sanded with sandpaper to remove dust, then wiped with anhydrous ethanol and left to dry to form a micro-roughened interface that facilitates adhesion.

[0053] Preparation of S3 repair sheet: Select uncured compound rubber with the same formula as the base material, calender it into 0.1-0.5mm sheet; cut it according to the shape of the curved surface color difference area.

[0054] S4 Bonding Interface Treatment: Apply hot-curing adhesive twice to the curved surface color difference area and the surface to be bonded with the repair sheet, and let stand until surface dry.

[0055] S5 Curved Surface Bonding and Air Exhaust: The repair sheet is gradually bonded from one side to the other along the curvature direction, manually compacted and the interface air is expelled to ensure uniform and continuous bonding.

[0056] S6 Apply an isolation and release layer: Cover the outer surface of the repair sheet with a heat-resistant isolation and release layer to avoid direct contact with the pressurized medium and leave marks, making it easier to remove later.

[0057] S7 Inflatable Bag Installation and Pressurization: Set an elastic inflatable bag on the outside of the repair area and fix it in place; inflate the inflatable bag to provide uniform surface pressure on the curved surface and apply it to the bonding interface.

[0058] S8 External Heating and Thermal Vulcanization: The repair area is heated in an external heating environment, and a stable temperature and pressure are maintained throughout the insulation stage, so that the repair sheet can be reliably vulcanized and bonded to the substrate under the action of the adhesive.

[0059] S9 depressurization and cooling: After vulcanization, depressurize and cool down, and remove the air bladder and isolation release layer.

[0060] S10 Inspection and Handling: Check the consistency of the surface color of the repaired area with the surrounding substrate, the surface flatness and the integrity of the adhesion, and perform edge trimming if necessary.

[0061] This embodiment uses "elastic air bladders and isolation release layers" to form continuous and uniform surface pressure on curved surfaces, reducing the risk of local indentation; external heating ensures that the interface reaches the vulcanization temperature of the rubber compound, thereby obtaining an appearance consistent with the substrate and stable interface bonding quality under inflation and pressurization conditions.

[0062] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for heat vulcanization repair of color differences on the surface of light-colored rubber products, characterized in that, include: a) Polish, clean, and dry the target surface where there is a color difference; b) Prepare a repair sheet using an unvulcanized compound rubber with the same formulation as the light-colored rubber sheet matrix, so that the repair sheet covers the color difference area and matches its shape; c) Apply hot-curing adhesive to the surface of the color difference area and the surface of the repair sheet to be bonded, respectively, and let them dry until surface dry; d) Align and bond the repair sheet with the color difference area and pre-press it; e) The bonding area is subjected to thermal vulcanization under pressure and heating conditions, wherein the pressure is applied by one of the following two methods: e1) Place the laminated light-colored rubber sheet into its molding mold, close the mold, apply pressure, and then heat-vulcanize; or e2) An elastic air bladder is provided on the outside of the fitting part and then inflated and pressurized before hot vulcanization.

2. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 1, characterized in that, The pressurization method involves placing the laminated light-colored rubber sheet into its original molding mold for mold closing, pressurization, and hot vulcanization.

3. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 1, characterized in that, The pressurization method involves setting an elastic air bladder on the outside of the bonding area and inflating it to apply pressure, so that the elastic air bladder provides uniform surface pressure to the bonding interface before hot vulcanization.

4. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 3, characterized in that, A heat-resistant insulating release layer is provided between the elastic inflatable bladder and the repair sheet to facilitate removal after heat vulcanization.

5. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 3 or 4, characterized in that, Hot vulcanization is carried out in an external heating environment to ensure that the bonding interface reaches the vulcanization temperature of the rubber compound.

6. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 1, characterized in that, The hot vulcanization conditions are: temperature 160℃±5℃, time 40min±5min, and vulcanization pressure 11~15MPa.

7. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 2, characterized in that, During the mold closing process, excess repair material overflows along the parting surface, forming a peelable thin flash.

8. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 1, characterized in that, The thickness of the repair sheet is 0.1 to 0.5 mm.

9. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 1, characterized in that, The repair sheet is prepared into a sheet shape by a rubber calender and then cut according to the shape of the color difference area.

10. The method for heat vulcanization repair of color difference on the surface of light-colored rubber products according to claim 1, characterized in that, In step a), the surface treatment involves hand or mechanical sanding with sandpaper to remove surface deposits and aging layers. After sanding, wipe with anhydrous ethanol and allow to air dry. In step c), the hot vulcanizing adhesive is applied in two coats and allowed to dry to surface dry before bonding.

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