JPH0222776B2 - - Google Patents

Description

[Detailed description of the invention]

Traditionally, hot melt adhesives have been made using a base resin such as ethylene-vinyl acetate copolymer (EVA) resin or polyamide resin, a tackifier made of various resins such as rosin or petroleum resin, and a low-melt material such as wax or paraffin. It was manufactured by hot-melting and mixing a modifying agent such as a fast-setting agent. Therefore, it has been impossible to obtain a hot melt adhesive having a heat resistance higher than the initial thermal melting point. The purpose of the present invention is to develop a hot melt adhesive that has heat resistance higher than the initial thermal melting temperature, and to impregnate an easy-to-process sheet-like base material with it to increase and equalize the adhesive force by making it into FRP. be. The present invention involves coating or impregnating a porous sheet base material with a plastisol in which a vinyl chloride paste resin is dispersed in a radically polymerizable liquid monomer or prepolymer, and leaving it at room temperature or heating it to prevent the surface from becoming sticky at room temperature. This is a method for producing a thermosetting hot melt adhesive sheet that is processed into a semi-gelled state to a certain degree. The radical polymerizable liquid monomers or prepolymers used in the present invention include diallyl phthalate (DAP) monomer, allyl acrylate, triallyl siamerate, diallyl maleate, dichloroallyl maleate, diallyl itaconate, diallyl sebacate, Allyl alcohol esters and acrylic esters such as diallyl adipate, diallyl malonate, diallyl glycolate, triallyl aconitate, diallyl monobutyl phosphate, diallyl monooctyl phosphate, triallyl phosphate, diallyl isophthalate, etc. Among these, most of the compounds in practical use have two double bonds, and have moderate compatibility with vinyl chloride paste resin. At the same time, a small amount of a radical polymerization catalyst such as an organic peroxide is added, and the heat during processing causes the plasticizer molecules to polymerize with each other, or some of them probably also react with vinyl chloride molecules. It may form a gel-like three-dimensional network structure to improve the product's hardness, heat distortion temperature,
It improves oil resistance, solvent resistance, chemical resistance, plasticizer migration resistance, etc. Specifically, DAP monomer (Osaka Soda), various types of Monocizer TD (Dainippon Ink Chemical), various types of aronics (Toagosei Chemical), etc. There is. In addition, in order to quickly cure the radical polymerizable liquid monomer or prepolymer, an organic peroxide is required as a radical polymerization catalyst, and hydrogen peroxide, hydroperoxides, dialkyl peroxides, diacyl peroxides, etc. , ketone peroxides, alkyl peresters, peroxydicarbonates, etc. are also required. Next, what is vinyl chloride paste resin?
Finely powdered vinyl chloride resin or vinyl chloride-vinyl acetate copolymer obtained by emulsion polymerization of vinyl chloride monomers, specifically Zeon 121 (PVC homopolymer, Nippon Zeon), Zeon 135 (PVC-vinyl acetate) These are vinyl chloride resins (paste resins) for plastisol that have been commercially available, such as Copolymer), Zeon 400 x 110A (carboxyl group-containing vinyl chloride polymer), and Sumirizto PXN (Sumitomo Chemical).
Among these, resins containing vinyl acetate groups or carboxy groups are suitable from the viewpoint of adhesion. Furthermore, in the present invention, a common plasticizer (primary plasticizer) can also be used in plastisol to improve the compatibility between the vinyl chloride paste resin and a radically polymerizable liquid monomer or prepolymer. as DOP,
There are various types such as phthalate esters such as DBP, phosphate esters such as TCP, and adipates such as DOA, as well as plasticizers/stabilizers such as polyesters and epoxys, and stabilizers such as metal soaps and inorganic acids. There are composite stabilizers such as salts, organic tin compounds, calcium-zinc type, cadmium organic composite, cadmium-barium type, etc., but liquid composite stabilizers are preferred. Inorganic fillers such as charcoal and silica powder can also be added if necessary. Next, suitable porous sheet substrates are mesh-like materials that are easily impregnated with plastisol, such as nonwoven fabrics, canola sheets, woven fabrics, and papers made of rayon or synthetic fibers. Further, as a coating or impregnating method, a known coating or impregnating method such as a spread coating method using reverse roll, knife, or curtain flow, or a dipping method can be applied. The coating or impregnating amount may be any desired amount, but 50 to 500 g/m ² (thickness 0.05 to 0.5 mm) is suitable for processing into a semi-gelled state. Due to its properties, plastisol has the following characteristics: (a) At room temperature, the surface of the resin particles is slightly solvated with plasticizer, but the particles move freely among each other and flow as a viscous sol (fluid state). ). However, (b) After aging in a plasticizer with high compatibility with the resin and low molecular weight at room temperature, or by heating in a normal plasticizer, the swelling of the resin particles progresses considerably and the particles are separated from each other. They loosely melt and solidify on the surface layer, and no longer have fluidity, but the center of the particle is ungelled, the physical strength of the gel is poor, and the surface is translucent with no gloss (semi-gelled state). ). When heated to a higher temperature, (c) the entire resin particle completely gels and swells to the core, melts and flows, and the solvated vinyl chloride molecules cause active micro-Brownian motion, causing the molecules between the particles to become entangled. The bond becomes stronger, the physical strength reaches its maximum, and the surface becomes glossy and transparent (completely molten state). Around this time, (d) the radical polymerization type liquid monomer or prepolymer reacts with the plasticizer molecules or some of them with the vinyl chloride molecules due to the action of a radical polymerization catalyst such as an organic peroxide. It forms a gel-like three-dimensional network structure, improving physical and chemical properties as well as adhesion (three-dimensional crosslinked state). The present invention takes advantage of the above-mentioned properties of plastisol to create (a) a porous plastisol that is easy to handle and has the effect of turning into FRP (fiber reinforced plastic) in the adhesive layer; (b) It is processed into a semi-gelled state by applying or impregnating it onto a sheet base material and leaving it at room temperature or heating it. Further, the obtained thermosetting hot melt adhesive sheet exhibits its function as an adhesive through (c) a completely melted state and (d) a three-dimensional crosslinked state. As a method for bringing liquid plastisol into a semi-gelled state, which is an important element in the present invention, a heating method is usually adopted from the viewpoint of workability. In order to obtain the half-life of the crosslinking agent consisting of peroxide, it is necessary to carry out the process at a temperature below the decomposition temperature and above the gelation temperature, and the type and amount of plasticizer,
Although it varies depending on the type and amount of paste resin, the type of organic peroxide, and the coating and impregnating film thickness,
It can usually be produced within a few minutes at a temperature in the range of 50 to 100°C. The thermosetting hot melt adhesive sheet produced in this way has a solid sheet shape with no stickiness on the surface at room temperature, and is easy to handle.
Because the heat melting temperature is low, it has good wettability to the adherend, and when heated continuously, the normal and heat-resistant adhesive strength improves, and it has properties not found in conventional hot melt adhesives, so honeycomb structures, It is useful as a structural adhesive or sealant for various adherends, such as bonding filter paper and metal plates. Next, the present invention will be explained by examples. Examples 1 and 2

[Table] The plastisol formulation shown in Table 1 was
Approximately 150 g/m ² on vinylon paper (non-woven fabric) of g/m ²
(thickness 0.15mm) and placed in a hot air dryer at 80℃ for 2 hours.
The thermosetting hot-melt adhesive sheet of the present invention was manufactured by passing the adhesive for a few minutes, cooling it to room temperature, and winding it up as it was. Next, a bonding area of 25 mm width x 12.5 mm was applied to a test piece for adhesion force measurement made of polished steel plate with a thickness of 0.2 mm x 25 mm width x 100 mm length.
Glue them together with a length of mm and press them with eyeball grips.
Table 2 shows the results of measuring the tensile shear adhesive strength at room temperature after being left at 170° C. for various hours and cured and molded.

【table】

Claims (1)

[Claims] 1 Apply or impregnate a porous sheet base material with a plastisol in which a vinyl chloride paste resin is dispersed in a radical polymerizable liquid monomer or prepolymer, leave it at room temperature or heat it, and half it to the extent that it does not become sticky at room temperature. A method for producing a thermosetting hot melt adhesive sheet, which is characterized by processing it into a gel state.