JPH0348236B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for producing a foamable hot melt adhesive which is in an unfoamed solid state at room temperature and expands in volume to form a foam after being heated and used. <Prior art and problems> Traditionally, hot melt adhesives have been made of a paste 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 wax. It was produced by hot-melting and mixing low-melting agents such as paraffin and modifiers such as fast-setting agents. Therefore, if a thermally decomposable foaming agent is mixed in, the hot melt adhesive will foam during production, so it is impossible to produce a foamable hot melt adhesive that is unfoamed at room temperature and forms a foam after heating. It was hot. <Object of the Invention> An object of the present invention is to provide a method for producing a foamable hot melt adhesive that is in an unfoamed solid state at room temperature and expands in volume to form a foam after being heated and used. <Disclosure of the invention> The present invention provides 50 to 200 parts by weight of a plasticizer for vinyl chloride and a thermally decomposable foaming agent with a decomposition temperature of 150 to 210°C to 100 parts by weight of a vinyl chloride paste resin.
Plastisol, which is liquid at room temperature with 0.1 to 20 parts by weight as an essential ingredient, is left at room temperature or heated to a semi-gelled state, and then processed into granules, pellets, or sheets to the extent that it does not become sticky at room temperature. This is a method for producing a foamable hot melt adhesive that is brought into a semi-gelled state. The vinyl chloride paste resin used in the present invention is a finely powdered vinyl chloride resin obtained by emulsion polymerization of vinyl chloride monomer alone and copolymerized vinyl acetate monomer, etc.
135,400×110A (manufactured by Nippon Zeon KK), Sumiritz
Known vinyl chloride paste resins such as PXN (manufactured by Sumitomo Chemical KK) may be used, but if adhesion, low-temperature melting properties, and low-temperature foaming moldability are required, vinyl chloride-vinyl acetate copolymers or carboxyl group-introduced resins may be used. It is better to mix resin. Plasticizers for vinyl chloride include phthalate esters such as DOP and DBP, phosphate esters such as TCP (tricresyl phosphate), adipates such as DOA (dioctyl adipate), chlorinated paraffin, and DAP (diallyl phthalate). In addition to monomers such as allyl ester thermosetting plasticizers, acrylic esters, unsaturated polyesters, etc.
Any known plasticizer that is compatible with vinyl chloride resin when heated, such as an epoxy-based plasticizer that acts as a stabilizer, may be used. What is a thermally decomposable blowing agent with a decomposition temperature of 150 to 210℃?
Foaming agents that generate decomposed gas when heated are available, including fine powders such as nitroso compounds, azo compounds such as azodicarbonamide and azobis/isobutyronitrile, and sulfonyl/hydrazide systems such as benzene/sulfonyl/hydrazide. However, azo compounds are commonly used. In addition to the above essential components, stabilizers for vinyl chloride are added to plastisol to stabilize complexes such as metal soaps, inorganic acid salts, organic tin compounds, calcium-zinc systems, cadmium organic complexes, and cadmium-barium systems. There are various stabilizers, but liquid composite stabilizers are preferred. Inorganic fillers such as charcoal and silica powder and fibers may also be added as required. Plastisol has these properties: (a) At room temperature, the surfaces of resin particles are slightly solvated with plasticizer, but the particles move freely among themselves and flow as a viscous sol. However, (b) in a plasticizer that has high compatibility with the resin and has a low molecular weight, the swelling of the resin particles progresses considerably after aging at room temperature, or when heated in a normal plasticizer. They melt together loosely on the surface layer and solidify,
Although fluidity is no longer lost, the center of the particle is partially gelled, 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 melts and swells to the core and flows, and the solvated vinyl chloride molecules cause active micro-Brownian motion, causing molecular entanglement between the particles. The relationship becomes stronger,
Its physical strength reaches its maximum, and the surface becomes glossy and transparent (completely molten state). Next, (d) in a completely molten state, the thermally decomposable foaming agent decomposes to generate gas and form a foam (foam forming state). The present invention takes advantage of the properties of plastisol as described above to convert (a) plastisol in a fluid state at room temperature, and (b)
It is processed into granules, pellets, or sheets before and after making it into a semi-gelled state. Further, the obtained foamable hot melt adhesive exhibits its function as an adhesive after passing through (c) a completely melted state and (d) a foamed state. The composition of plastisol, which is an important requirement in the present invention, is as described in the claims above. That is, the reason is the paste range
If the composition contains 50 parts by weight (PHR) or less of the plasticizer per 100 parts by weight, plastisol cannot be obtained in liquid form at room temperature, and if the composition contains 200 parts by weight (PHR) or more of the plasticizer, This is because even in a semi-gelled state, it remains sticky at room temperature. Next, the decomposition temperature of thermally decomposable foaming agents is 150°C to 210°C.The reason is that below 150°C, plastisol is in a completely molten state, and good foam cannot be obtained. Moreover, at a temperature of 210° C. or higher, the viscosity of the molten state is low and decomposition gas is released, making it impossible to obtain a good foam.
Next, the amount of foaming agent added is 0.1 to 20 parts by weight (PHR).The reason for this is that if it is less than 0.1 PHR, a foam cannot be obtained, and if it is more than 20 PHR, the foaming ratio will be too high or the undecomposed This is because the foaming agent remains, resulting in a decrease in adhesive strength. Next, as a method for converting plastisol, which is liquid at room temperature, into a semi-gelled state as described above, a heating method is usually adopted from the viewpoint of workability. It is necessary to carry out the process at a temperature below the decomposition temperature of the blowing agent and above the gelling temperature, which varies depending on the type and amount of plasticizer, the type and amount of paste resin, the type of blowing agent, and the film thickness. Usually 50~
It can be manufactured in a few minutes at a temperature of 100°C. For example, if you want to make it into granules, drop it into warm water. If it is desired to form a sheet, it may be coated on release paper using a knife coater or roll coater and passed through a hot air dryer. It can also be molded into any shape by pouring it thinly onto a hot plate, processing it into a semi-gelled state, and then cutting or crushing it. <Operations and Effects of the Invention> The foamable hot melt adhesive produced in this manner exhibits its function as a foam adhesive or sealant by heating to a complete melting temperature and above the decomposition temperature of the foaming agent. Normally 150~210℃
It performs its functions within the range of. It can be used as an adhesive for adherends with uneven surfaces, honeycomb structures, etc., and as a sealant for spot welds, etc.
It is useful as an adhesive sealant that requires adhesion to adherends, light weight, and void-filling properties. Next, the present invention will be explained by examples. Example 1

【table】

[Table] The plastisol formulation shown in Table 1 was coated on release paper using a knife coater at approximately 300 g/m ² (thickness
The foamable hot melt adhesive of the present invention was produced by applying the adhesive to a thickness of 0.3 mm), passing it through a hot air dryer at 80° C. for 3 minutes, cooling it to room temperature, and winding it up. Next, the meshed cement asbestos board surface and the embossed copper foil with an unevenness of 0.2 to 0.3 mm were
The foamable hot melt adhesive (sheet) was sandwiched and bonded for 5 minutes in a hot air dryer at 200°C. It was confirmed that the uneven parts of the adhesive layer after adhesive processing were completely filled with foam and adhesive processed.

Claims (1)

[Claims] 1. 50 to 200 parts by weight of a plasticizer for vinyl chloride and 0.1 to 20 parts by weight of a thermally decomposable blowing agent with a decomposition temperature of 150 to 210°C are essential components for 100 parts by weight of vinyl chloride paste resin. Plastisol, which is liquid at room temperature and has been prepared as a plastisol, is left at room temperature or heated to make it into a semi-gelled state, and then processed into granules, pellets, or sheets to make it into a semi-gelled state to the extent that it is not sticky at room temperature. A method for producing a foamable hot melt adhesive characterized by: 2. The method for producing a foamable hot melt adhesive according to claim 1, wherein the vinyl chloride paste resin contains a vinyl chloride-vinyl acetate copolymer or a carboxyl group-introduced resin.