JPS6234538B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for repairing the surface of a urethane molded product. Due to advances in molding machines, urethane molded products are now used in a wide range of applications in the form of solid (elastomer), hard and semi-hard integral skin foam, structural foam, and microcellular foam. When molding these materials, defects often occur on the surface depending on molding conditions and the like. For example, a urethane molded product formed by a molding method may have various defects on the surface of the molded product depending on molding conditions, mold shape, and other various factors. The main causes include unfilled areas that do not fill as per the mold shape due to the complexity of the mold shape and partially contain gas and solidify, air entrainment, and petal-like patterns called fluorocarbon flowers. On the other hand, the defective parts on the surface of the molded product are left as they are or are scratched with a knife, drill, etc. so that they can be easily repaired, and then a reactive substance for repair is applied along the shape of the molded product surface with a putty knife, spatula, etc. This has been leveled, repaired, and subjected to post-processing such as painting. At this time, the reactive substance for repair is highly sticky and will stick to putty knives, spatulas, etc., and if rubbed along the surface of the molded product, the repaired surface will be dented or streaked, so this process must be repeated and is time consuming. The reactive substance used for repair was attached to areas other than the repaired surface. Then, in order to remove what was attached to other than the repaired surface, the surface of the molded product was sometimes damaged when the reactive substance was scratched with a knife or sanded during or after curing. In addition, when the reactive material for repair is a soft material such as soft or semi-hard urethane, the force of scratching with a knife or the like may cause the repaired area to come off or be partially peeled off. The present invention improves the drawbacks of the above repair methods. In other words, a reactive substance for repair is filled into the concave defects on the surface of the urethane molded product, and a base material with good adhesion to the reactive substance (hereinafter referred to as adhesive base material) is applied and pressed to cause a repair reaction. A method for repairing the surface of a urethane molded product, which comprises removing the reactive substance that has spread outside the concave defect area together with the adhesive base material by peeling off the adhesive base material during or after the reaction cure. It is. To explain in detail, since urethane has good adhesive properties, it is common practice to apply a mold release agent to the surface of the mold before molding, and therefore a small amount of mold release agent is attached to the surface of the molded product. On the other hand, there is almost no mold release agent attached to the concave defect areas on the surface of the molded product, and the adhesion to the reactive substance for repair is good. Therefore, first, a reactive substance for repair is packed onto the repaired surface, an adhesive base material is applied on top of this, the reactive substance is pressed and held according to the shape of the molded product surface, and then the reactive substance is cured or after the reaction cures. The adhesive base material is torn off and the reactive substance that has spread outside the concave defect area is removed along with the adhesive base material. In this case, due to the mold release agent on the surface of the molded product, the adhesion between the reactive substance and the surface of the molded product is smaller than that of the adhesive base material, and as a result, the reactive substance that has spread outside the repaired surface adheres to the adhesive base material. death,
By tearing this off, it will be removed along with it.
At this time, the reactive substance on the repaired surface is firmly adhered to the molded article and is not removed together with the adhesive base material. In addition, if the dent in the defective area is shallow, the reactive substance for repair may be peeled off from the adhesive interface with the defective area when the adhesive base material is peeled off. Use a material that has good adhesion to the molded product and cure it sufficiently. Furthermore, by using a base material with weak adhesive strength as the adhesive base material, interfacial peeling of the reactive substance for repair can be prevented. In addition, if the adhesive force between the reactive substance for repair and the adhesive base material is too strong, cohesive failure may occur on the surface of the reactive substance for repair, but if the failure is in the surface layer, it can be repaired by simple polishing. It's not a problem because it can be done. Reactive substances for repair include, for example, compositions equivalent to the urethane molded product used, one-component and two-component urethane and silicone sealants, RTV rubber, and the like. More preferable products are those with a composition equivalent to that of urethane molded products, but with fillers added to increase the viscosity to make it easier to repair, those with a reduced amount of catalyst due to the repair time and number of uses, and those with flexible molded products that are flexible. This is a composition that has been slightly softened so that the repair adhesive surface is difficult to peel off. In the case of one-component urethane sealants and one-component silicone sealants, curing may be delayed if the adhesive base material used has poor moisture permeability or is difficult for solvents to volatilize. It is preferable to select and use a material with good moisture and solvent permeability, such as cloth, from among various adhesive base materials. Silicone sealants and RTV rubbers may not adhere well to the repaired surface and adhesive base material as they are, but in this case, to improve adhesion, apply a treatment agent such as Primer T (Shin-Etsu Silicone). It can be solved by doing. Examples of the adhesive substrate include cellophane tape, gummed tape, gummed cloth tape, vinyl tape, double-sided tape, adhesive film, paper tape, cloth, and wool. The timing for peeling off the adhesive substrate varies depending on the molded article to be repaired, but it is preferably during reaction curing. Examples will be described below, but the present invention is not limited thereto. Integral skin foam (semi-rigid product),
A hole approximately 3 mm deep was drilled with a 3 mmφ drill in a plate formed by a molding method using the following composition of structural foam and elastomer (low modulus product), and the following repairs were performed.

【table】

【table】

[Table] The following three reactive substances were used for repair. As shown in Formulation 1, 2, and 3 above, the composition is similar to that of the plate formed by the molding method, and silicon dioxide is mixed with a polyol component in a grease-like manner in order to reduce the amount of catalyst, increase the viscosity, and make it easier to repair. (hereinafter referred to as A). One-component urethane sealant (hereinafter referred to as B). RTV
Silicone rubber (using treatment agent) (hereinafter referred to as C).
Place these A, B, and C into the holes drilled in the board, and then use cellophane tape as an adhesive base.
Gum cloth tape, double-sided tape, adhesive film, or cloth is pressed against the surface of the patch plate and the reactive substance used for repair is in the process of reaction and curing (when it becomes hard to the touch), and the adhesive base material is peeled off and the surface to be repaired is removed. It was investigated whether the spread reactive substance would peel off along with the adhesive substrate. For comparison, repairs were carried out using conventional methods such as a putty knife and a spatula, and repairs were also carried out using polyethylene film. The results are shown in Table 1.

【table】

[Table] In the case of Comparative Example 1, the surface of the molded product was scratched when the reactive substance for repair was rubbed against the surface of the molded product using a putty knife, spatula, etc. In the case of Comparative Example 2, only the polyethylene film was peeled off, and the reactive substance that had spread outside the repaired surface remained on the surface of the molded product. In Examples 1 to 5, the reactive substance that had spread outside the repaired surface could be easily removed by peeling off the adhesive base material, and this effect was satisfied. In this way, according to the present invention, a reactive substance is filled on the repaired surface, an adhesive base material is applied and pressed, and by peeling it off, the reactive substance on the repaired surface is left behind, and the reactive substance spread around it is removed. By utilizing this method, reactive substances that have spread outside the repaired surface can be easily removed in a short period of time, and subsequent post-processing can be performed, thereby improving the drawbacks of conventional repair methods.

Claims (1)

[Claims] 1. In a method for repairing a concave defect formed on the surface of a urethane molded product formed using a mold coated with a mold release agent, the defect is filled with a reactive substance for repair, and then the above-mentioned After applying a reactive substance and a base material with good adhesion properties to the surface of the molded product, and then peeling off the base material during or after the reactive substance is cured, it is possible to spread the defect to areas other than the concave defects. A method for repairing the surface of a urethane molded product, characterized by removing ivy reactive substances together with the base material.